diff --git a/bench/src/async_compute.rs b/bench/src/async_compute.rs
index df0158ea..148ef394 100644
--- a/bench/src/async_compute.rs
+++ b/bench/src/async_compute.rs
@@ -37,7 +37,7 @@ fn bench_threadsafe_function(ctx: CallContext) -> Result<JsUndefined> {
   let tsfn = ctx.env.create_threadsafe_function(
     &callback,
     0,
-    |mut ctx: ThreadSafeCallContext<(usize, Ref<JsBufferValue>)>| {
+    |mut ctx: ThreadsafeCallContext<(usize, Ref<JsBufferValue>)>| {
       ctx
         .env
         .create_uint32(ctx.value.0 as u32)
diff --git a/bench/src/get_set_property.rs b/bench/src/get_set_property.rs
index 96779789..5a0219b5 100644
--- a/bench/src/get_set_property.rs
+++ b/bench/src/get_set_property.rs
@@ -40,7 +40,7 @@ impl FromStr for LineJoin {
 }
 
 pub fn register_js(exports: &mut JsObject, env: &Env) -> Result<()> {
-  let test_class = env.define_class(
+  let test_class = env.define_class::<bindgen_prelude::Unknown>(
     "TestClass",
     test_class_constructor,
     &[
diff --git a/bench/src/lib.rs b/bench/src/lib.rs
index 01d38976..19d3c7ca 100644
--- a/bench/src/lib.rs
+++ b/bench/src/lib.rs
@@ -1,4 +1,5 @@
 #![allow(clippy::uninlined_format_args)]
+#![allow(deprecated)]
 
 #[macro_use]
 extern crate napi_derive;
diff --git a/crates/backend/src/typegen.rs b/crates/backend/src/typegen.rs
index 4e853151..477c2fd4 100644
--- a/crates/backend/src/typegen.rs
+++ b/crates/backend/src/typegen.rs
@@ -212,6 +212,7 @@ static KNOWN_TYPES: Lazy<HashMap<&'static str, (&'static str, bool, bool)>> = La
     ("External", ("ExternalObject<{}>", false, false)),
     ("unknown", ("unknown", false, false)),
     ("Unknown", ("unknown", false, false)),
+    ("UnknownReturnValue", ("unknown", false, false)),
     ("JsUnknown", ("unknown", false, false)),
     ("This", ("this", false, false)),
     ("Rc", ("{}", false, false)),
@@ -338,6 +339,7 @@ pub fn ty_to_ts_type(
                 generic_ty,
                 index == 1 && is_generic_function_type(&rust_ty),
                 false,
+                // index == 2 is for ThreadsafeFunction with ErrorStrategy
                 is_generic_function_type(&rust_ty),
               ))
               .map(|(mut ty, is_optional)| {
@@ -346,6 +348,11 @@ pub fn ty_to_ts_type(
                 }
                 (ty, is_optional)
               }),
+              // const Generic for `ThreadsafeFunction` generic
+              syn::GenericArgument::Const(syn::Expr::Lit(syn::ExprLit {
+                lit: syn::Lit::Bool(bo),
+                ..
+              })) => Some((bo.value.to_string(), false)),
               _ => None,
             })
             .collect::<Vec<_>>()
@@ -408,15 +415,22 @@ pub fn ty_to_ts_type(
         {
           ts_ty = Some((t, false));
         } else if rust_ty == TSFN_RUST_TY {
-          let fatal_tsfn = match args.get(1) {
-            Some((arg, _)) => arg == "Fatal",
+          let fatal_tsfn = match args.last() {
+            Some((arg, _)) => arg == "false",
             _ => false,
           };
-          let args = args.first().map(|(arg, _)| arg).unwrap();
+          let fn_args = args.first().map(|(arg, _)| arg).unwrap();
+          let return_ty = args
+            .get(1)
+            .map(|(ty, _)| ty.clone())
+            .unwrap_or("any".to_owned());
           ts_ty = if fatal_tsfn {
-            Some((format!("({}) => any", args), false))
+            Some((format!("({fn_args}) => {return_ty}"), false))
           } else {
-            Some((format!("(err: Error | null, {}) => any", args), false))
+            Some((
+              format!("(err: Error | null, {fn_args}) => {return_ty}"),
+              false,
+            ))
           };
         } else {
           // there should be runtime registered type in else
diff --git a/crates/napi/src/async_work.rs b/crates/napi/src/async_work.rs
index 7a9a43e3..eebd3d95 100644
--- a/crates/napi/src/async_work.rs
+++ b/crates/napi/src/async_work.rs
@@ -114,11 +114,9 @@ unsafe extern "C" fn complete<T: Task>(
   let value = match value_ptr {
     Ok(v) => {
       let output = unsafe { v.assume_init() };
-      work
-        .inner_task
-        .resolve(unsafe { Env::from_raw(env) }, output)
+      work.inner_task.resolve(Env::from_raw(env), output)
     }
-    Err(e) => work.inner_task.reject(unsafe { Env::from_raw(env) }, e),
+    Err(e) => work.inner_task.reject(Env::from_raw(env), e),
   };
   if status != sys::Status::napi_cancelled && work.status.load(Ordering::Relaxed) != 2 {
     match check_status!(status)
@@ -144,7 +142,7 @@ unsafe extern "C" fn complete<T: Task>(
       }
     };
   }
-  if let Err(e) = work.inner_task.finally(unsafe { Env::from_raw(env) }) {
+  if let Err(e) = work.inner_task.finally(Env::from_raw(env)) {
     debug_assert!(false, "Panic in Task finally fn: {:?}", e);
   }
   let delete_status = unsafe { sys::napi_delete_async_work(env, napi_async_work) };
diff --git a/crates/napi/src/bindgen_runtime/js_values/date.rs b/crates/napi/src/bindgen_runtime/js_values/date.rs
index 689432fc..13fd4a73 100644
--- a/crates/napi/src/bindgen_runtime/js_values/date.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/date.rs
@@ -32,7 +32,7 @@ impl ValidateNapiValue for DateTime<Utc> {
 impl ToNapiValue for NaiveDateTime {
   unsafe fn to_napi_value(env: sys::napi_env, val: NaiveDateTime) -> Result<sys::napi_value> {
     let mut ptr = std::ptr::null_mut();
-    let millis_since_epoch_utc = val.timestamp_millis() as f64;
+    let millis_since_epoch_utc = val.and_utc().timestamp_millis() as f64;
 
     check_status!(
       unsafe { sys::napi_create_date(env, millis_since_epoch_utc, &mut ptr) },
@@ -145,11 +145,14 @@ impl FromNapiValue for DateTime<Utc> {
 
     let milliseconds_since_epoch_utc = milliseconds_since_epoch_utc as i64;
     let timestamp_seconds = milliseconds_since_epoch_utc / 1_000;
-    let naive = NaiveDateTime::from_timestamp_opt(
+    let naive = DateTime::from_timestamp(
       timestamp_seconds,
       (milliseconds_since_epoch_utc % 1_000 * 1_000_000) as u32,
     )
     .ok_or_else(|| Error::new(Status::DateExpected, "Found invalid date".to_owned()))?;
-    Ok(DateTime::<Utc>::from_naive_utc_and_offset(naive, Utc))
+    Ok(DateTime::<Utc>::from_naive_utc_and_offset(
+      naive.naive_utc(),
+      Utc,
+    ))
   }
 }
diff --git a/crates/napi/src/bindgen_runtime/js_values/function.rs b/crates/napi/src/bindgen_runtime/js_values/function.rs
index 53f572c0..eab1b2e4 100644
--- a/crates/napi/src/bindgen_runtime/js_values/function.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/function.rs
@@ -1,7 +1,11 @@
-use std::ptr;
+#![allow(deprecated)]
 
-use super::{FromNapiValue, ToNapiValue, TypeName, ValidateNapiValue};
+use std::{ptr, usize};
 
+use super::{FromNapiValue, ToNapiValue, TypeName, Unknown, ValidateNapiValue};
+
+#[cfg(feature = "napi4")]
+use crate::threadsafe_function::ThreadsafeFunction;
 pub use crate::JsFunction;
 use crate::{check_pending_exception, check_status, sys, Env, NapiRaw, Result, ValueType};
 
@@ -11,11 +15,82 @@ pub trait JsValuesTupleIntoVec {
   fn into_vec(self, env: sys::napi_env) -> Result<Vec<sys::napi_value>>;
 }
 
+impl<T: ToNapiValue> JsValuesTupleIntoVec for T {
+  #[allow(clippy::not_unsafe_ptr_arg_deref)]
+  fn into_vec(self, env: sys::napi_env) -> Result<Vec<sys::napi_value>> {
+    Ok(vec![unsafe {
+      <T as ToNapiValue>::to_napi_value(env, self)?
+    }])
+  }
+}
+
+pub trait TupleFromSliceValues {
+  #[allow(clippy::missing_safety_doc)]
+  unsafe fn from_slice_values(env: sys::napi_env, values: &[sys::napi_value]) -> Result<Self>
+  where
+    Self: Sized;
+}
+
+macro_rules! impl_tuple_conversion {
+  ($($ident:ident),*) => {
+    impl<$($ident: ToNapiValue),*> JsValuesTupleIntoVec for ($($ident,)*) {
+      #[allow(clippy::not_unsafe_ptr_arg_deref)]
+      fn into_vec(self, env: sys::napi_env) -> Result<Vec<sys::napi_value>> {
+        #[allow(non_snake_case)]
+        let ($($ident,)*) = self;
+        Ok(vec![$(unsafe { <$ident as ToNapiValue>::to_napi_value(env, $ident)? }),*])
+      }
+    }
+
+    impl<$($ident: FromNapiValue),*> TupleFromSliceValues for ($($ident,)*) {
+      unsafe fn from_slice_values(env: sys::napi_env, values: &[sys::napi_value]) -> $crate::Result<Self> {
+        #[allow(non_snake_case)]
+        let [$($ident),*] = values.try_into().map_err(|_| crate::Error::new(
+          crate::Status::InvalidArg,
+          "Invalid number of arguments",
+        ))?;
+        Ok(($(
+          unsafe { $ident::from_napi_value(env, $ident)?}
+        ,)*))
+      }
+    }
+  };
+}
+
+impl_tuple_conversion!(A);
+impl_tuple_conversion!(A, B);
+impl_tuple_conversion!(A, B, C);
+impl_tuple_conversion!(A, B, C, D);
+impl_tuple_conversion!(A, B, C, D, E);
+impl_tuple_conversion!(A, B, C, D, E, F);
+impl_tuple_conversion!(A, B, C, D, E, F, G);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X);
+impl_tuple_conversion!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y);
+impl_tuple_conversion!(
+  A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z
+);
+
 /// A JavaScript function.
 /// It can only live in the scope of a function call.
 /// If you want to use it outside the scope of a function call, you can turn it into a reference.
 /// By calling the `create_ref` method.
-pub struct Function<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> {
+pub struct Function<'scope, Args: JsValuesTupleIntoVec = Unknown, Return = Unknown> {
   pub(crate) env: sys::napi_env,
   pub(crate) value: sys::napi_value,
   pub(crate) _args: std::marker::PhantomData<Args>,
@@ -23,9 +98,7 @@ pub struct Function<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> {
   _scope: std::marker::PhantomData<&'scope ()>,
 }
 
-impl<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> TypeName
-  for Function<'scope, Args, Return>
-{
+impl<'scope, Args: JsValuesTupleIntoVec, Return> TypeName for Function<'scope, Args, Return> {
   fn type_name() -> &'static str {
     "Function"
   }
@@ -35,17 +108,13 @@ impl<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> TypeName
   }
 }
 
-impl<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> NapiRaw
-  for Function<'scope, Args, Return>
-{
+impl<'scope, Args: JsValuesTupleIntoVec, Return> NapiRaw for Function<'scope, Args, Return> {
   unsafe fn raw(&self) -> sys::napi_value {
     self.value
   }
 }
 
-impl<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> FromNapiValue
-  for Function<'scope, Args, Return>
-{
+impl<'scope, Args: JsValuesTupleIntoVec, Return> FromNapiValue for Function<'scope, Args, Return> {
   unsafe fn from_napi_value(env: sys::napi_env, value: sys::napi_value) -> Result<Self> {
     Ok(Function {
       env,
@@ -57,11 +126,70 @@ impl<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> FromNapiValue
   }
 }
 
-impl<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> ValidateNapiValue
+impl<'scope, Args: JsValuesTupleIntoVec, Return> ValidateNapiValue
   for Function<'scope, Args, Return>
 {
 }
 
+impl<'scope, Args: JsValuesTupleIntoVec, Return> Function<'scope, Args, Return> {
+  /// Get the name of the JavaScript function.
+  pub fn name(&self) -> Result<String> {
+    let mut name = ptr::null_mut();
+    check_status!(
+      unsafe {
+        sys::napi_get_named_property(self.env, self.value, "name\0".as_ptr().cast(), &mut name)
+      },
+      "Get function name failed"
+    )?;
+    unsafe { String::from_napi_value(self.env, name) }
+  }
+
+  /// Create a reference to the JavaScript function.
+  pub fn create_ref(&self) -> Result<FunctionRef<Args, Return>> {
+    let mut reference = ptr::null_mut();
+    check_status!(
+      unsafe { sys::napi_create_reference(self.env, self.value, 1, &mut reference) },
+      "Create reference failed"
+    )?;
+    Ok(FunctionRef {
+      inner: reference,
+      env: self.env,
+      _args: std::marker::PhantomData,
+      _return: std::marker::PhantomData,
+    })
+  }
+
+  /// Create a new instance of the JavaScript Class.
+  pub fn new_instance(&self, args: Args) -> Result<Unknown> {
+    let mut raw_instance = ptr::null_mut();
+    let mut args = args.into_vec(self.env)?;
+    check_status!(
+      unsafe {
+        sys::napi_new_instance(
+          self.env,
+          self.value,
+          args.len(),
+          args.as_mut_ptr().cast(),
+          &mut raw_instance,
+        )
+      },
+      "Create new instance failed"
+    )?;
+    unsafe { Unknown::from_napi_value(self.env, raw_instance) }
+  }
+
+  #[cfg(feature = "napi4")]
+  /// Create a threadsafe function from the JavaScript function.
+  pub fn build_threadsafe_function(&self) -> ThreadsafeFunctionBuilder<Args, Return> {
+    ThreadsafeFunctionBuilder {
+      env: self.env,
+      value: self.value,
+      _args: std::marker::PhantomData,
+      _return: std::marker::PhantomData,
+    }
+  }
+}
+
 impl<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> Function<'scope, Args, Return> {
   /// Call the JavaScript function.
   /// `this` in the JavaScript function will be `undefined`.
@@ -97,8 +225,7 @@ impl<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> Function<'scope,
     let raw_this = unsafe { Context::to_napi_value(self.env, this) }?;
     let args_ptr = args.into_vec(self.env)?;
     let mut raw_return = ptr::null_mut();
-    check_pending_exception!(
-      self.env,
+    check_status!(
       unsafe {
         sys::napi_call_function(
           self.env,
@@ -113,35 +240,66 @@ impl<'scope, Args: JsValuesTupleIntoVec, Return: FromNapiValue> Function<'scope,
     )?;
     unsafe { Return::from_napi_value(self.env, raw_return) }
   }
+}
 
-  /// Create a reference to the JavaScript function.
-  pub fn create_ref(&self) -> Result<FunctionRef<Args, Return>> {
-    let mut reference = ptr::null_mut();
-    check_status!(
-      unsafe { sys::napi_create_reference(self.env, self.value, 1, &mut reference) },
-      "Create reference failed"
-    )?;
-    Ok(FunctionRef {
-      inner: reference,
+pub struct ThreadsafeFunctionBuilder<
+  Args: JsValuesTupleIntoVec,
+  Return,
+  const Weak: bool = false,
+  const MaxQueueSize: usize = 0,
+> {
+  pub(crate) env: sys::napi_env,
+  pub(crate) value: sys::napi_value,
+  _args: std::marker::PhantomData<Args>,
+  _return: std::marker::PhantomData<Return>,
+}
+
+impl<
+    Args: JsValuesTupleIntoVec,
+    Return: FromNapiValue,
+    const Weak: bool,
+    const MaxQueueSize: usize,
+  > ThreadsafeFunctionBuilder<Args, Return, Weak, MaxQueueSize>
+{
+  pub fn weak<const NewWeak: bool>(
+    self,
+  ) -> ThreadsafeFunctionBuilder<Args, Return, NewWeak, MaxQueueSize> {
+    ThreadsafeFunctionBuilder {
       env: self.env,
+      value: self.value,
       _args: std::marker::PhantomData,
       _return: std::marker::PhantomData,
-    })
+    }
+  }
+
+  pub fn max_queue_size<const NewMaxQueueSize: usize>(
+    self,
+  ) -> ThreadsafeFunctionBuilder<Args, Return, Weak, NewMaxQueueSize> {
+    ThreadsafeFunctionBuilder {
+      env: self.env,
+      value: self.value,
+      _args: std::marker::PhantomData,
+      _return: std::marker::PhantomData,
+    }
+  }
+
+  pub fn build(self) -> Result<ThreadsafeFunction<Args, Return, false, Weak, MaxQueueSize>> {
+    unsafe { ThreadsafeFunction::from_napi_value(self.env, self.value) }
   }
 }
 
 /// A reference to a JavaScript function.
 /// It can be used to outlive the scope of the function.
-pub struct FunctionRef<Args: JsValuesTupleIntoVec, Return: FromNapiValue> {
+pub struct FunctionRef<Args: JsValuesTupleIntoVec, Return> {
   pub(crate) inner: sys::napi_ref,
   pub(crate) env: sys::napi_env,
   _args: std::marker::PhantomData<Args>,
   _return: std::marker::PhantomData<Return>,
 }
 
-unsafe impl<Args: JsValuesTupleIntoVec, Return: FromNapiValue> Sync for FunctionRef<Args, Return> {}
+unsafe impl<Args: JsValuesTupleIntoVec, Return> Sync for FunctionRef<Args, Return> {}
 
-impl<Args: JsValuesTupleIntoVec, Return: FromNapiValue> FunctionRef<Args, Return> {
+impl<Args: JsValuesTupleIntoVec, Return> FunctionRef<Args, Return> {
   pub fn borrow_back<'scope>(&self, env: &'scope Env) -> Result<Function<'scope, Args, Return>> {
     let mut value = ptr::null_mut();
     check_status!(
@@ -158,14 +316,14 @@ impl<Args: JsValuesTupleIntoVec, Return: FromNapiValue> FunctionRef<Args, Return
   }
 }
 
-impl<Args: JsValuesTupleIntoVec, Return: FromNapiValue> Drop for FunctionRef<Args, Return> {
+impl<Args: JsValuesTupleIntoVec, Return> Drop for FunctionRef<Args, Return> {
   fn drop(&mut self) {
     let status = unsafe { sys::napi_delete_reference(self.env, self.inner) };
     debug_assert_eq!(status, sys::Status::napi_ok, "Drop FunctionRef failed");
   }
 }
 
-impl<Args: JsValuesTupleIntoVec, Return: FromNapiValue> TypeName for FunctionRef<Args, Return> {
+impl<Args: JsValuesTupleIntoVec, Return> TypeName for FunctionRef<Args, Return> {
   fn type_name() -> &'static str {
     "Function"
   }
@@ -175,9 +333,7 @@ impl<Args: JsValuesTupleIntoVec, Return: FromNapiValue> TypeName for FunctionRef
   }
 }
 
-impl<Args: JsValuesTupleIntoVec, Return: FromNapiValue> FromNapiValue
-  for FunctionRef<Args, Return>
-{
+impl<Args: JsValuesTupleIntoVec, Return> FromNapiValue for FunctionRef<Args, Return> {
   unsafe fn from_napi_value(env: sys::napi_env, value: sys::napi_value) -> Result<Self> {
     let mut reference = ptr::null_mut();
     check_status!(
@@ -198,6 +354,55 @@ impl<Args: JsValuesTupleIntoVec, Return: FromNapiValue> ValidateNapiValue
 {
 }
 
+pub struct FunctionCallContext<'scope> {
+  pub(crate) args: &'scope [sys::napi_value],
+  pub(crate) this: sys::napi_value,
+  pub(crate) env: &'scope mut Env,
+}
+
+impl FunctionCallContext<'_> {
+  /// Get the number of arguments from the JavaScript function call.
+  pub fn length(&self) -> usize {
+    self.args.len()
+  }
+
+  /// Get the first argument from the JavaScript function call.
+  pub fn first_arg<T: FromNapiValue>(&self) -> Result<T> {
+    if self.args.is_empty() {
+      return Err(crate::Error::new(
+        crate::Status::InvalidArg,
+        "There is no arguments",
+      ));
+    }
+    unsafe { T::from_napi_value(self.env.0, self.args[0]) }
+  }
+
+  /// Get the arguments from the JavaScript function call.
+  /// The arguments will be converted to a tuple.
+  /// If the number of arguments is not equal to the number of tuple elements, an error will be returned.
+  /// example:
+  /// ```rust
+  /// let (num, string) = ctx.args::<(u32, String)>()?;
+  /// ````
+  pub fn args<Args: TupleFromSliceValues>(&self) -> Result<Args> {
+    unsafe { Args::from_slice_values(self.env.0, self.args) }
+  }
+
+  /// Get the arguments Vec from the JavaScript function call.
+  pub fn arguments<T: FromNapiValue>(&self) -> Result<Vec<T>> {
+    self
+      .args
+      .iter()
+      .map(|arg| unsafe { <T as FromNapiValue>::from_napi_value(self.env.0, *arg) })
+      .collect::<Result<Vec<T>>>()
+  }
+
+  /// Get the `this` from the JavaScript function call.
+  pub fn this<This: FromNapiValue>(&self) -> Result<This> {
+    unsafe { This::from_napi_value(self.env.0, self.this) }
+  }
+}
+
 macro_rules! impl_call_apply {
   ($fn_call_name:ident, $fn_apply_name:ident, $($ident:ident),*) => {
     #[allow(non_snake_case, clippy::too_many_arguments)]
@@ -205,7 +410,7 @@ macro_rules! impl_call_apply {
       &self,
       $($ident: $ident),*
     ) -> Result<Return> {
-      let raw_this = unsafe { Env::from_raw(self.0.env) }
+      let raw_this = Env::from_raw(self.0.env)
         .get_undefined()
         .map(|u| unsafe { u.raw() })?;
 
@@ -284,7 +489,7 @@ impl JsFunction {
   }
 
   pub fn call0<Return: FromNapiValue>(&self) -> Result<Return> {
-    let raw_this = unsafe { Env::from_raw(self.0.env) }
+    let raw_this = Env::from_raw(self.0.env)
       .get_undefined()
       .map(|u| unsafe { u.raw() })?;
 
diff --git a/crates/napi/src/bindgen_runtime/js_values/task.rs b/crates/napi/src/bindgen_runtime/js_values/task.rs
index f4facfa5..e3fa8aba 100644
--- a/crates/napi/src/bindgen_runtime/js_values/task.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/task.rs
@@ -3,7 +3,7 @@ use std::ptr;
 use std::rc::Rc;
 use std::sync::atomic::{AtomicPtr, AtomicU8, Ordering};
 
-use super::{FromNapiValue, ToNapiValue, TypeName};
+use super::{FromNapiValue, ToNapiValue, TypeName, Unknown};
 use crate::{
   async_work, check_status, sys, Env, Error, JsError, JsObject, NapiValue, Status, Task,
 };
@@ -65,7 +65,7 @@ impl FromNapiValue for AbortSignal {
       raw_deferred: raw_promise.clone(),
       status: task_status.clone(),
     };
-    let js_env = unsafe { Env::from_raw(env) };
+    let js_env = Env::from_raw(env);
     check_status!(unsafe {
       sys::napi_wrap(
         env,
@@ -76,7 +76,10 @@ impl FromNapiValue for AbortSignal {
         ptr::null_mut(),
       )
     })?;
-    signal.set_named_property("onabort", js_env.create_function("onabort", on_abort)?)?;
+    signal.set_named_property(
+      "onabort",
+      js_env.create_function::<Unknown, Unknown>("onabort", on_abort)?,
+    )?;
     Ok(AbortSignal {
       raw_work: async_work_inner,
       raw_deferred: raw_promise,
diff --git a/crates/napi/src/bindgen_runtime/mod.rs b/crates/napi/src/bindgen_runtime/mod.rs
index 97605869..b3acec2d 100644
--- a/crates/napi/src/bindgen_runtime/mod.rs
+++ b/crates/napi/src/bindgen_runtime/mod.rs
@@ -35,7 +35,7 @@ pub unsafe extern "C" fn raw_finalize_unchecked<T: ObjectFinalize>(
   _finalize_hint: *mut c_void,
 ) {
   let data: Box<T> = unsafe { Box::from_raw(finalize_data.cast()) };
-  if let Err(err) = data.finalize(unsafe { Env::from_raw(env) }) {
+  if let Err(err) = data.finalize(Env::from_raw(env)) {
     let e: JsError = err.into();
     unsafe { e.throw_into(env) };
     return;
diff --git a/crates/napi/src/env.rs b/crates/napi/src/env.rs
index 31526e76..83eb58cc 100644
--- a/crates/napi/src/env.rs
+++ b/crates/napi/src/env.rs
@@ -7,9 +7,26 @@ use std::mem;
 use std::os::raw::{c_char, c_void};
 use std::ptr;
 
-use crate::bindgen_runtime::FromNapiValue;
+#[cfg(feature = "serde-json")]
+use serde::de::DeserializeOwned;
+#[cfg(feature = "serde-json")]
+use serde::Serialize;
+
+#[cfg(feature = "napi8")]
+use crate::async_cleanup_hook::AsyncCleanupHook;
+#[cfg(feature = "napi5")]
+use crate::bindgen_runtime::FunctionCallContext;
 #[cfg(feature = "napi4")]
 use crate::bindgen_runtime::ToNapiValue;
+use crate::bindgen_runtime::{FromNapiValue, Function, JsValuesTupleIntoVec, Unknown};
+#[cfg(feature = "napi3")]
+use crate::cleanup_env::{CleanupEnvHook, CleanupEnvHookData};
+#[cfg(feature = "serde-json")]
+use crate::js_values::{De, Ser};
+#[cfg(feature = "napi4")]
+use crate::threadsafe_function::{ThreadsafeCallContext, ThreadsafeFunction};
+#[cfg(feature = "napi3")]
+use crate::JsError;
 use crate::{
   async_work::{self, AsyncWorkPromise},
   check_status,
@@ -19,21 +36,6 @@ use crate::{
   Error, ExtendedErrorInfo, NodeVersion, Result, Status, ValueType,
 };
 
-#[cfg(feature = "napi8")]
-use crate::async_cleanup_hook::AsyncCleanupHook;
-#[cfg(feature = "napi3")]
-use crate::cleanup_env::{CleanupEnvHook, CleanupEnvHookData};
-#[cfg(feature = "serde-json")]
-use crate::js_values::{De, Ser};
-#[cfg(feature = "napi4")]
-use crate::threadsafe_function::{ThreadSafeCallContext, ThreadsafeFunction};
-#[cfg(feature = "napi3")]
-use crate::JsError;
-#[cfg(feature = "serde-json")]
-use serde::de::DeserializeOwned;
-#[cfg(feature = "serde-json")]
-use serde::Serialize;
-
 pub type Callback = unsafe extern "C" fn(sys::napi_env, sys::napi_callback_info) -> sys::napi_value;
 
 pub(crate) static EMPTY_VEC: Vec<u8> = vec![];
@@ -58,7 +60,7 @@ impl From<sys::napi_env> for Env {
 
 impl Env {
   #[allow(clippy::missing_safety_doc)]
-  pub unsafe fn from_raw(env: sys::napi_env) -> Self {
+  pub fn from_raw(env: sys::napi_env) -> Self {
     Env(env)
   }
 
@@ -189,12 +191,7 @@ impl Env {
   pub fn create_string_latin1(&self, chars: &[u8]) -> Result<JsString> {
     let mut raw_value = ptr::null_mut();
     check_status!(unsafe {
-      sys::napi_create_string_latin1(
-        self.0,
-        chars.as_ptr() as *const _,
-        chars.len(),
-        &mut raw_value,
-      )
+      sys::napi_create_string_latin1(self.0, chars.as_ptr().cast(), chars.len(), &mut raw_value)
     })?;
     Ok(unsafe { JsString::from_raw_unchecked(self.0, raw_value) })
   }
@@ -570,14 +567,17 @@ impl Env {
   /// The newly created function is not automatically visible from script after this call.
   ///
   /// Instead, a property must be explicitly set on any object that is visible to JavaScript, in order for the function to be accessible from script.
-  pub fn create_function(&self, name: &str, callback: Callback) -> Result<JsFunction> {
+  pub fn create_function<Args: JsValuesTupleIntoVec, Return>(
+    &self,
+    name: &str,
+    callback: Callback,
+  ) -> Result<Function<Args, Return>> {
     let mut raw_result = ptr::null_mut();
     let len = name.len();
-    let name = CString::new(name)?;
     check_status!(unsafe {
       sys::napi_create_function(
         self.0,
-        name.as_ptr(),
+        name.as_ptr().cast(),
         len,
         Some(callback),
         ptr::null_mut(),
@@ -585,26 +585,29 @@ impl Env {
       )
     })?;
 
-    Ok(unsafe { JsFunction::from_raw_unchecked(self.0, raw_result) })
+    unsafe { Function::<Args, Return>::from_napi_value(self.0, raw_result) }
   }
 
   #[cfg(feature = "napi5")]
-  pub fn create_function_from_closure<R, F>(&self, name: &str, callback: F) -> Result<JsFunction>
+  pub fn create_function_from_closure<Args: JsValuesTupleIntoVec, Return, F>(
+    &self,
+    name: &str,
+    callback: F,
+  ) -> Result<Function<Args, Return>>
   where
-    F: 'static + Fn(crate::CallContext<'_>) -> Result<R>,
-    R: ToNapiValue,
+    Return: ToNapiValue,
+    F: 'static + Fn(FunctionCallContext) -> Result<Return>,
   {
     let closure_data_ptr = Box::into_raw(Box::new(callback));
 
     let mut raw_result = ptr::null_mut();
     let len = name.len();
-    let name = CString::new(name)?;
     check_status!(unsafe {
       sys::napi_create_function(
         self.0,
-        name.as_ptr(),
+        name.as_ptr().cast(),
         len,
-        Some(trampoline::<R, F>),
+        Some(trampoline::<Return, F>),
         closure_data_ptr.cast(), // We let it borrow the data here
         &mut raw_result,
       )
@@ -629,7 +632,7 @@ impl Env {
       )
     })?;
 
-    Ok(unsafe { JsFunction::from_raw_unchecked(self.0, raw_result) })
+    unsafe { Function::from_napi_value(self.0, raw_result) }
   }
 
   /// This API retrieves a napi_extended_error_info structure with information about the last error that occurred.
@@ -740,12 +743,12 @@ impl Env {
   }
 
   /// Create JavaScript class
-  pub fn define_class(
+  pub fn define_class<Args: JsValuesTupleIntoVec>(
     &self,
     name: &str,
     constructor_cb: Callback,
     properties: &[Property],
-  ) -> Result<JsFunction> {
+  ) -> Result<Function<Args, Unknown>> {
     let mut raw_result = ptr::null_mut();
     let raw_properties = properties
       .iter()
@@ -755,7 +758,7 @@ impl Env {
     check_status!(unsafe {
       sys::napi_define_class(
         self.0,
-        c_name.as_ptr() as *const c_char,
+        c_name.as_ptr().cast(),
         name.len(),
         Some(constructor_cb),
         ptr::null_mut(),
@@ -765,7 +768,7 @@ impl Env {
       )
     })?;
 
-    Ok(unsafe { JsFunction::from_raw_unchecked(self.0, raw_result) })
+    unsafe { Function::from_napi_value(self.0, raw_result) }
   }
 
   #[allow(clippy::needless_pass_by_ref_mut)]
@@ -1055,17 +1058,22 @@ impl Env {
   }
 
   #[cfg(feature = "napi4")]
+  #[deprecated(
+    since = "2.17.0",
+    note = "Please use `Function::build_threadsafe_function` instead"
+  )]
+  #[allow(deprecated)]
   pub fn create_threadsafe_function<
     T: Send,
     V: ToNapiValue,
-    R: 'static + Send + FnMut(ThreadSafeCallContext<T>) -> Result<Vec<V>>,
+    R: 'static + Send + FnMut(ThreadsafeCallContext<T>) -> Result<Vec<V>>,
   >(
     &self,
     func: &JsFunction,
-    max_queue_size: usize,
+    _max_queue_size: usize,
     callback: R,
   ) -> Result<ThreadsafeFunction<T>> {
-    ThreadsafeFunction::create(self.0, func.0.value, max_queue_size, callback)
+    ThreadsafeFunction::create(self.0, func.0.value, callback)
   }
 
   #[cfg(all(feature = "tokio_rt", feature = "napi4"))]
@@ -1403,7 +1411,7 @@ unsafe extern "C" fn set_instance_finalize_callback<T, Hint, F>(
 {
   let (value, callback) = unsafe { *Box::from_raw(finalize_data as *mut (TaggedObject<T>, F)) };
   let hint = unsafe { *Box::from_raw(finalize_hint as *mut Hint) };
-  let env = unsafe { Env::from_raw(raw_env) };
+  let env = Env::from_raw(raw_env);
   callback(FinalizeContext {
     value: value.object.unwrap(),
     hint,
@@ -1425,7 +1433,7 @@ unsafe extern "C" fn raw_finalize_with_custom_callback<Hint, Finalize>(
   Finalize: FnOnce(Hint, Env),
 {
   let (hint, callback) = unsafe { *Box::from_raw(finalize_hint as *mut (Hint, Finalize)) };
-  callback(hint, unsafe { Env::from_raw(env) });
+  callback(hint, Env::from_raw(env));
 }
 
 #[cfg(feature = "napi8")]
@@ -1449,22 +1457,20 @@ unsafe extern "C" fn async_finalize<Arg, F>(
 
 #[cfg(feature = "napi5")]
 pub(crate) unsafe extern "C" fn trampoline<
-  R: ToNapiValue,
-  F: Fn(crate::CallContext) -> Result<R>,
+  Return: ToNapiValue,
+  F: Fn(FunctionCallContext) -> Result<Return>,
 >(
   raw_env: sys::napi_env,
   cb_info: sys::napi_callback_info,
 ) -> sys::napi_value {
-  use crate::CallContext;
+  // Fast path for 4 arguments or less.
+  let mut argc = 4;
+  let mut raw_args = Vec::with_capacity(4);
+  let mut raw_this = ptr::null_mut();
+  let mut closure_data_ptr = ptr::null_mut();
 
-  let (raw_this, raw_args, closure_data_ptr, argc) = {
-    // Fast path for 4 arguments or less.
-    let mut argc = 4;
-    let mut raw_args = Vec::with_capacity(4);
-    let mut raw_this = ptr::null_mut();
-    let mut closure_data_ptr = ptr::null_mut();
-
-    let status = unsafe {
+  check_status!(
+    unsafe {
       sys::napi_get_cb_info(
         raw_env,
         cb_info,
@@ -1473,45 +1479,45 @@ pub(crate) unsafe extern "C" fn trampoline<
         &mut raw_this,
         &mut closure_data_ptr,
       )
-    };
-    debug_assert!(
-      Status::from(status) == Status::Ok,
-      "napi_get_cb_info failed"
-    );
-
+    },
+    "napi_get_cb_info failed"
+  )
+  .and_then(|_| {
     // Arguments length greater than 4, resize the vector.
     if argc > 4 {
       raw_args = vec![ptr::null_mut(); argc];
-      let status = unsafe {
-        sys::napi_get_cb_info(
-          raw_env,
-          cb_info,
-          &mut argc,
-          raw_args.as_mut_ptr(),
-          &mut raw_this,
-          &mut closure_data_ptr,
-        )
-      };
-      debug_assert!(
-        Status::from(status) == Status::Ok,
+      check_status!(
+        unsafe {
+          sys::napi_get_cb_info(
+            raw_env,
+            cb_info,
+            &mut argc,
+            raw_args.as_mut_ptr(),
+            &mut raw_this,
+            &mut closure_data_ptr,
+          )
+        },
         "napi_get_cb_info failed"
-      );
+      )?;
     } else {
       unsafe { raw_args.set_len(argc) };
     }
-
-    (raw_this, raw_args, closure_data_ptr, argc)
-  };
-
-  let closure: &F = Box::leak(unsafe { Box::from_raw(closure_data_ptr.cast()) });
-  let mut env = unsafe { Env::from_raw(raw_env) };
-  let call_context = CallContext::new(&mut env, cb_info, raw_this, raw_args.as_slice(), argc);
-  closure(call_context)
-    .and_then(|ret: R| unsafe { <R as ToNapiValue>::to_napi_value(env.0, ret) })
-    .unwrap_or_else(|e| {
-      unsafe { JsError::from(e).throw_into(raw_env) };
-      ptr::null_mut()
+    Ok((raw_this, raw_args, closure_data_ptr, argc))
+  })
+  .and_then(|(raw_this, raw_args, closure_data_ptr, _argc)| {
+    let closure: &F = Box::leak(unsafe { Box::from_raw(closure_data_ptr.cast()) });
+    let mut env = Env::from_raw(raw_env);
+    closure(FunctionCallContext {
+      env: &mut env,
+      this: raw_this,
+      args: raw_args.as_slice(),
     })
+  })
+  .and_then(|ret| unsafe { <Return as ToNapiValue>::to_napi_value(raw_env, ret) })
+  .unwrap_or_else(|e| {
+    unsafe { JsError::from(e).throw_into(raw_env) };
+    ptr::null_mut()
+  })
 }
 
 #[cfg(feature = "napi5")]
@@ -1551,7 +1557,7 @@ pub(crate) unsafe extern "C" fn trampoline_setter<
   };
 
   let closure: &F = Box::leak(unsafe { Box::from_raw(closure_data_ptr.cast()) });
-  let env = unsafe { Env::from_raw(raw_env) };
+  let env = Env::from_raw(raw_env);
   raw_args
     .first()
     .ok_or_else(|| Error::new(Status::InvalidArg, "Missing argument in property setter"))
@@ -1602,7 +1608,7 @@ pub(crate) unsafe extern "C" fn trampoline_getter<
   };
 
   let closure: &F = Box::leak(unsafe { Box::from_raw(closure_data_ptr.cast()) });
-  let env = unsafe { Env::from_raw(raw_env) };
+  let env = Env::from_raw(raw_env);
   closure(env, unsafe {
     crate::bindgen_runtime::Object::from_raw_unchecked(raw_env, raw_this)
   })
diff --git a/crates/napi/src/error.rs b/crates/napi/src/error.rs
index ce4db4cc..db35ed08 100644
--- a/crates/napi/src/error.rs
+++ b/crates/napi/src/error.rs
@@ -20,7 +20,7 @@ pub type Result<T, S = Status> = std::result::Result<T, Error<S>>;
 /// Represent `JsError`.
 /// Return this Error in `js_function`, **napi-rs** will throw it as `JsError` for you.
 /// If you want throw it as `TypeError` or `RangeError`, you can use `JsTypeError/JsRangeError::from(Error).throw_into(env)`
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct Error<S: AsRef<str> = Status> {
   pub status: S,
   pub reason: String,
@@ -28,6 +28,17 @@ pub struct Error<S: AsRef<str> = Status> {
   pub(crate) maybe_raw: sys::napi_ref,
 }
 
+impl<S: AsRef<str>> std::fmt::Debug for Error<S> {
+  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    write!(
+      f,
+      "Error {{ status: {:?}, reason: {:?} }}",
+      self.status.as_ref(),
+      self.reason
+    )
+  }
+}
+
 impl<S: AsRef<str>> ToNapiValue for Error<S> {
   unsafe fn to_napi_value(env: sys::napi_env, val: Self) -> Result<sys::napi_value> {
     if val.maybe_raw.is_null() {
@@ -358,7 +369,13 @@ macro_rules! check_status_and_type {
         let value_type = $crate::type_of!($env, $val)?;
         let error_msg = match value_type {
           ValueType::Function => {
-            let function_name = unsafe { JsFunction::from_raw_unchecked($env, $val).name()? };
+            let function_name = unsafe {
+              $crate::bindgen_prelude::Function::<
+                $crate::bindgen_prelude::Unknown,
+                $crate::bindgen_prelude::Unknown,
+              >::from_napi_value($env, $val)?
+              .name()?
+            };
             format!(
               $msg,
               format!(
diff --git a/crates/napi/src/js_values/deferred.rs b/crates/napi/src/js_values/deferred.rs
index 8cde0dc9..0e32e812 100644
--- a/crates/napi/src/js_values/deferred.rs
+++ b/crates/napi/src/js_values/deferred.rs
@@ -23,7 +23,7 @@ struct DeferredTrace(sys::napi_ref);
 #[cfg(feature = "deferred_trace")]
 impl DeferredTrace {
   fn new(raw_env: sys::napi_env) -> Result<Self> {
-    let env = unsafe { Env::from_raw(raw_env) };
+    let env = Env::from_raw(raw_env);
     let reason = env.create_string("none").unwrap();
 
     let mut js_error = ptr::null_mut();
@@ -42,7 +42,7 @@ impl DeferredTrace {
   }
 
   fn into_rejected(self, raw_env: sys::napi_env, err: Error) -> Result<sys::napi_value> {
-    let env = unsafe { Env::from_raw(raw_env) };
+    let env = Env::from_raw(raw_env);
     let mut raw = ptr::null_mut();
     check_status!(
       unsafe { sys::napi_get_reference_value(raw_env, self.0, &mut raw) },
@@ -210,7 +210,7 @@ extern "C" fn napi_resolve_deferred<Data: ToNapiValue, Resolver: FnOnce(Env) ->
   let deferred_data: Box<DeferredData<Data, Resolver>> = unsafe { Box::from_raw(data.cast()) };
   let result = deferred_data
     .resolver
-    .and_then(|resolver| resolver(unsafe { Env::from_raw(env) }))
+    .and_then(|resolver| resolver(Env::from_raw(env)))
     .and_then(|res| unsafe { ToNapiValue::to_napi_value(env, res) });
 
   if let Err(e) = result.and_then(|res| {
diff --git a/crates/napi/src/js_values/function.rs b/crates/napi/src/js_values/function.rs
index ce19fe6a..734131e5 100644
--- a/crates/napi/src/js_values/function.rs
+++ b/crates/napi/src/js_values/function.rs
@@ -4,12 +4,13 @@ use super::Value;
 #[cfg(feature = "napi4")]
 use crate::{
   bindgen_runtime::ToNapiValue,
-  threadsafe_function::{ThreadSafeCallContext, ThreadsafeFunction},
+  threadsafe_function::{ThreadsafeCallContext, ThreadsafeFunction},
 };
 use crate::{bindgen_runtime::TypeName, JsString};
 use crate::{check_pending_exception, ValueType};
 use crate::{sys, Env, Error, JsObject, JsUnknown, NapiRaw, NapiValue, Result, Status};
 
+#[deprecated(since = "2.17.0", note = "Please use `Function` instead")]
 pub struct JsFunction(pub(crate) Value);
 
 impl TypeName for JsFunction {
@@ -45,7 +46,7 @@ impl JsFunction {
     let raw_this = this
       .map(|v| unsafe { v.raw() })
       .or_else(|| {
-        unsafe { Env::from_raw(self.0.env) }
+        Env::from_raw(self.0.env)
           .get_undefined()
           .ok()
           .map(|u| unsafe { u.raw() })
@@ -76,7 +77,7 @@ impl JsFunction {
     let raw_this = this
       .map(|v| unsafe { v.raw() })
       .or_else(|| {
-        unsafe { Env::from_raw(self.0.env) }
+        Env::from_raw(self.0.env)
           .get_undefined()
           .ok()
           .map(|u| unsafe { u.raw() })
@@ -138,17 +139,24 @@ impl JsFunction {
   }
 
   #[cfg(feature = "napi4")]
-  pub fn create_threadsafe_function<T, V, F, ES>(
+  pub fn create_threadsafe_function<
+    T,
+    V,
+    Return,
+    F,
+    const ES: bool,
+    const Weak: bool,
+    const MaxQueueSize: usize,
+  >(
     &self,
-    max_queue_size: usize,
     callback: F,
-  ) -> Result<ThreadsafeFunction<T, ES>>
+  ) -> Result<ThreadsafeFunction<T, Return, ES, Weak, MaxQueueSize>>
   where
     T: 'static,
+    Return: crate::bindgen_runtime::FromNapiValue,
     V: ToNapiValue,
-    F: 'static + Send + FnMut(ThreadSafeCallContext<T>) -> Result<Vec<V>>,
-    ES: crate::threadsafe_function::ErrorStrategy::T,
+    F: 'static + Send + FnMut(ThreadsafeCallContext<T>) -> Result<Vec<V>>,
   {
-    ThreadsafeFunction::create(self.0.env, self.0.value, max_queue_size, callback)
+    ThreadsafeFunction::create(self.0.env, self.0.value, callback)
   }
 }
diff --git a/crates/napi/src/js_values/global.rs b/crates/napi/src/js_values/global.rs
index 12a58b94..61e37661 100644
--- a/crates/napi/src/js_values/global.rs
+++ b/crates/napi/src/js_values/global.rs
@@ -1,7 +1,8 @@
-use std::convert::TryInto;
-
 use super::*;
-use crate::{bindgen_runtime::FromNapiValue, Env};
+use crate::{
+  bindgen_runtime::{FromNapiValue, Function},
+  threadsafe_function::UnknownReturnValue,
+};
 
 pub struct JsGlobal(pub(crate) Value);
 
@@ -21,56 +22,41 @@ impl FromNapiValue for JSON {
 
 impl JSON {
   pub fn stringify<V: NapiRaw>(&self, value: V) -> Result<std::string::String> {
-    let func: JsFunction = self.get_named_property_unchecked("stringify")?;
-    let result = func
-      .call(None, &[value])
-      .map(|ret| unsafe { ret.cast::<JsString>() })?;
-    result.into_utf8()?.as_str().map(|s| s.to_owned())
+    let func: Function<V, std::string::String> = self.get_named_property_unchecked("stringify")?;
+    func.call(value)
   }
 }
 
 impl JsGlobal {
-  pub fn set_interval(&self, handler: JsFunction, interval: f64) -> Result<JsTimeout> {
-    let func: JsFunction = self.get_named_property_unchecked("setInterval")?;
-    func
-      .call(
-        None,
-        &[
-          handler.into_unknown(),
-          unsafe { Env::from_raw(self.0.env) }
-            .create_double(interval)?
-            .into_unknown(),
-        ],
-      )
-      .and_then(|ret| ret.try_into())
+  pub fn set_interval(
+    &self,
+    handler: Function<(), UnknownReturnValue>,
+    interval: f64,
+  ) -> Result<JsTimeout> {
+    let func: Function<(Function<(), UnknownReturnValue>, f64), JsTimeout> =
+      self.get_named_property_unchecked("setInterval")?;
+    func.call((handler, interval))
   }
 
   pub fn clear_interval(&self, timer: JsTimeout) -> Result<JsUndefined> {
-    let func: JsFunction = self.get_named_property_unchecked("clearInterval")?;
-    func
-      .call(None, &[timer.into_unknown()])
-      .and_then(|ret| ret.try_into())
+    let func: Function<JsTimeout, JsUndefined> =
+      self.get_named_property_unchecked("clearInterval")?;
+    func.call(timer)
   }
 
-  pub fn set_timeout(&self, handler: JsFunction, interval: f64) -> Result<JsTimeout> {
-    let func: JsFunction = self.get_named_property_unchecked("setTimeout")?;
-    func
-      .call(
-        None,
-        &[
-          handler.into_unknown(),
-          unsafe { Env::from_raw(self.0.env) }
-            .create_double(interval)?
-            .into_unknown(),
-        ],
-      )
-      .and_then(|ret| ret.try_into())
+  pub fn set_timeout(
+    &self,
+    handler: Function<(), UnknownReturnValue>,
+    interval: f64,
+  ) -> Result<JsTimeout> {
+    let func: Function<(Function<(), UnknownReturnValue>, f64), JsTimeout> =
+      self.get_named_property_unchecked("setTimeout")?;
+    func.call((handler, interval))
   }
 
   pub fn clear_timeout(&self, timer: JsTimeout) -> Result<JsUndefined> {
-    let func: JsFunction = self.get_named_property_unchecked("clearTimeout")?;
-    func
-      .call(None, &[timer.into_unknown()])
-      .and_then(|ret| ret.try_into())
+    let func: Function<JsTimeout, JsUndefined> =
+      self.get_named_property_unchecked("clearTimeout")?;
+    func.call(timer)
   }
 }
diff --git a/crates/napi/src/js_values/mod.rs b/crates/napi/src/js_values/mod.rs
index 2deeffa8..a660241a 100644
--- a/crates/napi/src/js_values/mod.rs
+++ b/crates/napi/src/js_values/mod.rs
@@ -1,3 +1,5 @@
+#![allow(deprecated)]
+
 use std::convert::TryFrom;
 #[cfg(feature = "napi5")]
 use std::ffi::c_void;
diff --git a/crates/napi/src/js_values/object.rs b/crates/napi/src/js_values/object.rs
index 77507f00..eb1e05e9 100644
--- a/crates/napi/src/js_values/object.rs
+++ b/crates/napi/src/js_values/object.rs
@@ -76,7 +76,7 @@ unsafe extern "C" fn finalize_callback<T, Hint, F>(
   let (value, callback, raw_ref) =
     unsafe { *Box::from_raw(finalize_data as *mut (T, F, sys::napi_ref)) };
   let hint = unsafe { *Box::from_raw(finalize_hint as *mut Hint) };
-  let env = unsafe { Env::from_raw(raw_env) };
+  let env = Env::from_raw(raw_env);
   callback(FinalizeContext { env, value, hint });
   if !raw_ref.is_null() {
     let status = unsafe { sys::napi_delete_reference(raw_env, raw_ref) };
diff --git a/crates/napi/src/js_values/ser.rs b/crates/napi/src/js_values/ser.rs
index 75316d2f..9a53b2ba 100644
--- a/crates/napi/src/js_values/ser.rs
+++ b/crates/napi/src/js_values/ser.rs
@@ -308,7 +308,7 @@ impl ser::SerializeSeq for SeqSerializer {
   where
     T: Serialize,
   {
-    let env = unsafe { Env::from_raw(self.array.0.env) };
+    let env = Env::from_raw(self.array.0.env);
     self.array.set_element(
       self.current_index as _,
       JsUnknown(value.serialize(Ser::new(&env))?),
@@ -331,7 +331,7 @@ impl ser::SerializeTuple for SeqSerializer {
   where
     T: Serialize,
   {
-    let env = unsafe { Env::from_raw(self.array.0.env) };
+    let env = Env::from_raw(self.array.0.env);
     self.array.set_element(
       self.current_index as _,
       JsUnknown(value.serialize(Ser::new(&env))?),
@@ -354,7 +354,7 @@ impl ser::SerializeTupleStruct for SeqSerializer {
   where
     T: Serialize,
   {
-    let env = unsafe { Env::from_raw(self.array.0.env) };
+    let env = Env::from_raw(self.array.0.env);
     self.array.set_element(
       self.current_index as _,
       JsUnknown(value.serialize(Ser::new(&env))?),
@@ -377,7 +377,7 @@ impl ser::SerializeTupleVariant for SeqSerializer {
   where
     T: Serialize,
   {
-    let env = unsafe { Env::from_raw(self.array.0.env) };
+    let env = Env::from_raw(self.array.0.env);
     self.array.set_element(
       self.current_index as _,
       JsUnknown(value.serialize(Ser::new(&env))?),
@@ -405,7 +405,7 @@ impl ser::SerializeMap for MapSerializer {
   where
     T: Serialize,
   {
-    let env = unsafe { Env::from_raw(self.obj.0.env) };
+    let env = Env::from_raw(self.obj.0.env);
     self.key = JsString(key.serialize(Ser::new(&env))?);
     Ok(())
   }
@@ -414,7 +414,7 @@ impl ser::SerializeMap for MapSerializer {
   where
     T: Serialize,
   {
-    let env = unsafe { Env::from_raw(self.obj.0.env) };
+    let env = Env::from_raw(self.obj.0.env);
     self.obj.set_property(
       JsString(Value {
         env: self.key.0.env,
@@ -435,7 +435,7 @@ impl ser::SerializeMap for MapSerializer {
     K: Serialize,
     V: Serialize,
   {
-    let env = unsafe { Env::from_raw(self.obj.0.env) };
+    let env = Env::from_raw(self.obj.0.env);
     self.obj.set_property(
       JsString(key.serialize(Ser::new(&env))?),
       JsUnknown(value.serialize(Ser::new(&env))?),
@@ -461,7 +461,7 @@ impl ser::SerializeStruct for StructSerializer {
   where
     T: Serialize,
   {
-    let env = unsafe { Env::from_raw(self.obj.0.env) };
+    let env = Env::from_raw(self.obj.0.env);
     self
       .obj
       .set_named_property(key, JsUnknown(value.serialize(Ser::new(&env))?))?;
@@ -482,7 +482,7 @@ impl ser::SerializeStructVariant for StructSerializer {
   where
     T: Serialize,
   {
-    let env = unsafe { Env::from_raw(self.obj.0.env) };
+    let env = Env::from_raw(self.obj.0.env);
     self
       .obj
       .set_named_property(key, JsUnknown(value.serialize(Ser::new(&env))?))?;
diff --git a/crates/napi/src/task.rs b/crates/napi/src/task.rs
index 96ba80c9..1d5d9ce4 100644
--- a/crates/napi/src/task.rs
+++ b/crates/napi/src/task.rs
@@ -13,13 +13,15 @@ pub trait Task: Send + Sized {
   /// Into this method if `compute` return `Ok`
   fn resolve(&mut self, env: Env, output: Self::Output) -> Result<Self::JsValue>;
 
+  #[allow(unused_variables)]
   /// Into this method if `compute` return `Err`
-  fn reject(&mut self, _env: Env, err: Error) -> Result<Self::JsValue> {
+  fn reject(&mut self, env: Env, err: Error) -> Result<Self::JsValue> {
     Err(err)
   }
 
-  // after resolve or reject
-  fn finally(&mut self, _env: Env) -> Result<()> {
+  #[allow(unused_variables)]
+  /// after resolve or reject
+  fn finally(&mut self, env: Env) -> Result<()> {
     Ok(())
   }
 }
diff --git a/crates/napi/src/threadsafe_function.rs b/crates/napi/src/threadsafe_function.rs
index 41df54d4..c16e9097 100644
--- a/crates/napi/src/threadsafe_function.rs
+++ b/crates/napi/src/threadsafe_function.rs
@@ -1,21 +1,26 @@
 #![allow(clippy::single_component_path_imports)]
 
 use std::convert::Into;
-use std::ffi::CString;
 use std::marker::PhantomData;
 use std::os::raw::c_void;
 use std::ptr::{self, null_mut};
-use std::sync::atomic::{AtomicBool, AtomicPtr, Ordering};
-use std::sync::{Arc, RwLock, RwLockWriteGuard, Weak};
+use std::sync::{
+  self,
+  atomic::{AtomicBool, AtomicPtr, Ordering},
+  Arc, RwLock, RwLockWriteGuard,
+};
 
 use crate::bindgen_runtime::{
-  FromNapiValue, JsValuesTupleIntoVec, ToNapiValue, TypeName, ValidateNapiValue,
+  FromNapiValue, JsValuesTupleIntoVec, ToNapiValue, TypeName, Unknown, ValidateNapiValue,
 };
-use crate::{check_status, sys, Env, JsError, JsUnknown, Result, Status};
+use crate::{check_status, sys, Env, Error, JsError, Result, Status};
+
+#[deprecated(since = "2.17.0", note = "Please use `ThreadsafeFunction` instead")]
+pub type ThreadSafeCallContext<T> = ThreadsafeCallContext<T>;
 
 /// ThreadSafeFunction Context object
 /// the `value` is the value passed to `call` method
-pub struct ThreadSafeCallContext<T: 'static> {
+pub struct ThreadsafeCallContext<T: 'static> {
   pub env: Env,
   pub value: T,
 }
@@ -36,68 +41,6 @@ impl From<ThreadsafeFunctionCallMode> for sys::napi_threadsafe_function_call_mod
   }
 }
 
-type_level_enum! {
-  /// Type-level `enum` to express how to feed [`ThreadsafeFunction`] errors to
-  /// the inner [`JsFunction`].
-  ///
-  /// ### Context
-  ///
-  /// For callbacks that expect a `Result`-like kind of input, the convention is
-  /// to have the callback take an `error` parameter as its first parameter.
-  ///
-  /// This way receiving a `Result<Args…>` can be modelled as follows:
-  ///
-  ///   - In case of `Err(error)`, feed that `error` entity as the first parameter
-  ///     of the callback;
-  ///
-  ///   - Otherwise (in case of `Ok(_)`), feed `null` instead.
-  ///
-  /// In pseudo-code:
-  ///
-  /// ```rust,ignore
-  /// match result_args {
-  ///     Ok(args) => {
-  ///         let js_null = /* … */;
-  ///         callback.call(
-  ///             // this
-  ///             None,
-  ///             // args…
-  ///             &iter::once(js_null).chain(args).collect::<Vec<_>>(),
-  ///         )
-  ///     },
-  ///     Err(err) => callback.call(None, &[JsError::from(err)]),
-  /// }
-  /// ```
-  ///
-  /// **Note that the `Err` case can stem from a failed conversion from native
-  /// values to js values when calling the callback!**
-  ///
-  /// That's why:
-  ///
-  /// > **[This][`ErrorStrategy::CalleeHandled`] is the default error strategy**.
-  ///
-  /// In order to opt-out of it, [`ThreadsafeFunction`] has an optional second
-  /// generic parameter (of "kind" [`ErrorStrategy::T`]) that defines whether
-  /// this behavior ([`ErrorStrategy::CalleeHandled`]) or a non-`Result` one
-  /// ([`ErrorStrategy::Fatal`]) is desired.
-  pub enum ErrorStrategy {
-    /// Input errors (including conversion errors) are left for the callee to
-    /// handle:
-    ///
-    /// The callee receives an extra `error` parameter (the first one), which is
-    /// `null` if no error occurred, and the error payload otherwise.
-    CalleeHandled,
-
-    /// Input errors (including conversion errors) are deemed fatal:
-    ///
-    /// they can thus cause a `panic!` or abort the process.
-    ///
-    /// The callee thus is not expected to have to deal with [that extra `error`
-    /// parameter][CalleeHandled], which is thus not added.
-    Fatal,
-  }
-}
-
 struct ThreadsafeFunctionHandle {
   raw: AtomicPtr<sys::napi_threadsafe_function__>,
   aborted: RwLock<bool>,
@@ -178,10 +121,10 @@ enum ThreadsafeFunctionCallVariant {
   WithCallback,
 }
 
-struct ThreadsafeFunctionCallJsBackData<T> {
+struct ThreadsafeFunctionCallJsBackData<T, Return = Unknown> {
   data: T,
   call_variant: ThreadsafeFunctionCallVariant,
-  callback: Box<dyn FnOnce(Result<JsUnknown>) -> Result<()>>,
+  callback: Box<dyn FnOnce(Result<Return>, Env) -> Result<()>>,
 }
 
 /// Communicate with the addon's main thread by invoking a JavaScript function from other threads.
@@ -190,58 +133,70 @@ struct ThreadsafeFunctionCallJsBackData<T> {
 /// An example of using `ThreadsafeFunction`:
 ///
 /// ```rust
-/// #[macro_use]
-/// extern crate napi_derive;
-///
 /// use std::thread;
 ///
 /// use napi::{
 ///     threadsafe_function::{
 ///         ThreadSafeCallContext, ThreadsafeFunctionCallMode, ThreadsafeFunctionReleaseMode,
 ///     },
-///     CallContext, Error, JsFunction, JsNumber, JsUndefined, Result, Status,
 /// };
+/// use napi_derive::napi;
 ///
-/// #[js_function(1)]
-/// pub fn test_threadsafe_function(ctx: CallContext) -> Result<JsUndefined> {
-///   let func = ctx.get::<JsFunction>(0)?;
-///
-///   let tsfn =
-///       ctx
-///           .env
-///           .create_threadsafe_function(&func, 0, |ctx: ThreadSafeCallContext<Vec<u32>>| {
-///             ctx.value
-///                 .iter()
-///                 .map(|v| ctx.env.create_uint32(*v))
-///                 .collect::<Result<Vec<JsNumber>>>()
-///           })?;
-///
+/// #[napi]
+/// pub fn call_threadsafe_function(callback: ThreadsafeFunction<(u32, bool, String), ()>) {
 ///   let tsfn_cloned = tsfn.clone();
 ///
 ///   thread::spawn(move || {
 ///       let output: Vec<u32> = vec![0, 1, 2, 3];
 ///       // It's okay to call a threadsafe function multiple times.
-///       tsfn.call(Ok(output.clone()), ThreadsafeFunctionCallMode::Blocking);
+///       tsfn.call(Ok((1, false, "NAPI-RS".into())), ThreadsafeFunctionCallMode::Blocking);
+///       tsfn.call(Ok((2, true, "NAPI-RS".into())), ThreadsafeFunctionCallMode::NonBlocking);
 ///   });
 ///
 ///   thread::spawn(move || {
-///       let output: Vec<u32> = vec![3, 2, 1, 0];
-///       // It's okay to call a threadsafe function multiple times.
-///       tsfn_cloned.call(Ok(output.clone()), ThreadsafeFunctionCallMode::NonBlocking);
+///       tsfn_cloned.call((3, false, "NAPI-RS".into())), ThreadsafeFunctionCallMode::NonBlocking);
 ///   });
-///
-///   ctx.env.get_undefined()
 /// }
 /// ```
-pub struct ThreadsafeFunction<T: 'static, ES: ErrorStrategy::T = ErrorStrategy::CalleeHandled> {
+pub struct ThreadsafeFunction<
+  T: 'static,
+  Return: FromNapiValue + 'static = Unknown,
+  const CalleeHandled: bool = true,
+  const Weak: bool = false,
+  const MaxQueueSize: usize = 0,
+> {
   handle: Arc<ThreadsafeFunctionHandle>,
-  _phantom: PhantomData<(T, ES)>,
+  _phantom: PhantomData<(T, Return)>,
 }
 
-unsafe impl<T: 'static, ES: ErrorStrategy::T> Send for ThreadsafeFunction<T, ES> {}
-unsafe impl<T: 'static, ES: ErrorStrategy::T> Sync for ThreadsafeFunction<T, ES> {}
+unsafe impl<
+    T: 'static,
+    Return: FromNapiValue,
+    const CalleeHandled: bool,
+    const Weak: bool,
+    const MaxQueueSize: usize,
+  > Send for ThreadsafeFunction<T, Return, { CalleeHandled }, { Weak }, { MaxQueueSize }>
+{
+}
 
-impl<T: 'static, ES: ErrorStrategy::T> Clone for ThreadsafeFunction<T, ES> {
+unsafe impl<
+    T: 'static,
+    Return: FromNapiValue,
+    const CalleeHandled: bool,
+    const Weak: bool,
+    const MaxQueueSize: usize,
+  > Sync for ThreadsafeFunction<T, Return, { CalleeHandled }, { Weak }, { MaxQueueSize }>
+{
+}
+
+impl<
+    T: 'static,
+    Return: FromNapiValue,
+    const CalleeHandled: bool,
+    const Weak: bool,
+    const MaxQueueSize: usize,
+  > Clone for ThreadsafeFunction<T, Return, { CalleeHandled }, { Weak }, { MaxQueueSize }>
+{
   fn clone(&self) -> Self {
     self.handle.with_read_aborted(|aborted| {
       if aborted {
@@ -256,86 +211,67 @@ impl<T: 'static, ES: ErrorStrategy::T> Clone for ThreadsafeFunction<T, ES> {
   }
 }
 
-impl<T: ToNapiValue> JsValuesTupleIntoVec for T {
-  #[allow(clippy::not_unsafe_ptr_arg_deref)]
-  fn into_vec(self, env: sys::napi_env) -> Result<Vec<sys::napi_value>> {
-    Ok(vec![unsafe {
-      <T as ToNapiValue>::to_napi_value(env, self)?
-    }])
-  }
-}
-
-macro_rules! impl_js_value_tuple_to_vec {
-  ($($ident:ident),*) => {
-    impl<$($ident: ToNapiValue),*> JsValuesTupleIntoVec for ($($ident,)*) {
-      #[allow(clippy::not_unsafe_ptr_arg_deref)]
-      fn into_vec(self, env: sys::napi_env) -> Result<Vec<sys::napi_value>> {
-        #[allow(non_snake_case)]
-        let ($($ident,)*) = self;
-        Ok(vec![$(unsafe { <$ident as ToNapiValue>::to_napi_value(env, $ident)? }),*])
-      }
-    }
-  };
-}
-
-impl_js_value_tuple_to_vec!(A);
-impl_js_value_tuple_to_vec!(A, B);
-impl_js_value_tuple_to_vec!(A, B, C);
-impl_js_value_tuple_to_vec!(A, B, C, D);
-impl_js_value_tuple_to_vec!(A, B, C, D, E);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W);
-impl_js_value_tuple_to_vec!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X);
-impl_js_value_tuple_to_vec!(
-  A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y
-);
-impl_js_value_tuple_to_vec!(
-  A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z
-);
-
-impl<T: JsValuesTupleIntoVec + 'static, ES: ErrorStrategy::T> FromNapiValue
-  for ThreadsafeFunction<T, ES>
+impl<
+    T: JsValuesTupleIntoVec + 'static,
+    Return: FromNapiValue,
+    const CalleeHandled: bool,
+    const Weak: bool,
+    const MaxQueueSize: usize,
+  > FromNapiValue for ThreadsafeFunction<T, Return, { CalleeHandled }, { Weak }, { MaxQueueSize }>
 {
   unsafe fn from_napi_value(env: sys::napi_env, napi_val: sys::napi_value) -> Result<Self> {
-    Self::create(env, napi_val, 0, |ctx| ctx.value.into_vec(ctx.env.0))
+    Self::create(env, napi_val, |ctx| ctx.value.into_vec(ctx.env.0))
   }
 }
 
-impl<T: 'static, ES: ErrorStrategy::T> ThreadsafeFunction<T, ES> {
-  /// See [napi_create_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_create_threadsafe_function)
-  /// for more information.
+impl<
+    T: 'static,
+    Return: FromNapiValue,
+    const CalleeHandled: bool,
+    const Weak: bool,
+    const MaxQueueSize: usize,
+  > ThreadsafeFunction<T, Return, { CalleeHandled }, { Weak }, { MaxQueueSize }>
+{
+  // See [napi_create_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_create_threadsafe_function)
+  // for more information.
   pub(crate) fn create<
     V: ToNapiValue,
-    R: 'static + Send + FnMut(ThreadSafeCallContext<T>) -> Result<Vec<V>>,
+    R: 'static + Send + FnMut(ThreadsafeCallContext<T>) -> Result<Vec<V>>,
   >(
     env: sys::napi_env,
     func: sys::napi_value,
-    max_queue_size: usize,
     callback: R,
   ) -> Result<Self> {
     let mut async_resource_name = ptr::null_mut();
-    let s = "napi_rs_threadsafe_function";
-    let len = s.len();
-    let s = CString::new(s)?;
-    check_status!(unsafe {
-      sys::napi_create_string_utf8(env, s.as_ptr(), len, &mut async_resource_name)
-    })?;
+    static THREAD_SAFE_FUNCTION_ASYNC_RESOURCE_NAME: &str = "napi_rs_threadsafe_function";
+
+    #[cfg(feature = "experimental")]
+    {
+      check_status!(unsafe {
+        let mut copied = false;
+        sys::node_api_create_external_string_latin1(
+          env,
+          THREAD_SAFE_FUNCTION_ASYNC_RESOURCE_NAME.as_ptr().cast(),
+          27,
+          None,
+          ptr::null_mut(),
+          &mut async_resource_name,
+          &mut copied,
+        )
+      })?;
+    }
+
+    #[cfg(not(feature = "experimental"))]
+    {
+      check_status!(unsafe {
+        sys::napi_create_string_utf8(
+          env,
+          THREAD_SAFE_FUNCTION_ASYNC_RESOURCE_NAME.as_ptr().cast(),
+          27,
+          &mut async_resource_name,
+        )
+      })?;
+    }
 
     let mut raw_tsfn = ptr::null_mut();
     let callback_ptr = Box::into_raw(Box::new(callback));
@@ -346,23 +282,35 @@ impl<T: 'static, ES: ErrorStrategy::T> ThreadsafeFunction<T, ES> {
         func,
         ptr::null_mut(),
         async_resource_name,
-        max_queue_size,
+        MaxQueueSize,
         1,
-        Arc::downgrade(&handle).into_raw() as *mut c_void, // pass handler to thread_finalize_cb
+        Arc::downgrade(&handle).into_raw().cast_mut().cast(), // pass handler to thread_finalize_cb
         Some(thread_finalize_cb::<T, V, R>),
         callback_ptr.cast(),
-        Some(call_js_cb::<T, V, R, ES>),
+        Some(call_js_cb::<T, Return, V, R, CalleeHandled>),
         &mut raw_tsfn,
       )
     })?;
     handle.set_raw(raw_tsfn);
 
+    // Weak ThreadsafeFunction will not prevent the event loop from exiting
+    if Weak {
+      check_status!(
+        unsafe { sys::napi_unref_threadsafe_function(env, raw_tsfn) },
+        "Unref threadsafe function failed in Weak mode"
+      )?;
+    }
+
     Ok(ThreadsafeFunction {
       handle,
       _phantom: PhantomData,
     })
   }
 
+  #[deprecated(
+    since = "2.17.0",
+    note = "Please use `ThreadsafeFunction::clone` instead of manually increasing the reference count"
+  )]
   /// See [napi_ref_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_ref_threadsafe_function)
   /// for more information.
   ///
@@ -377,6 +325,10 @@ impl<T: 'static, ES: ErrorStrategy::T> ThreadsafeFunction<T, ES> {
     })
   }
 
+  #[deprecated(
+    since = "2.17.0",
+    note = "Please use `ThreadsafeFunction::clone` instead of manually decreasing the reference count"
+  )]
   /// See [napi_unref_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_unref_threadsafe_function)
   /// for more information.
   pub fn unref(&mut self, env: &Env) -> Result<()> {
@@ -395,6 +347,10 @@ impl<T: 'static, ES: ErrorStrategy::T> ThreadsafeFunction<T, ES> {
     self.handle.with_read_aborted(|aborted| aborted)
   }
 
+  #[deprecated(
+    since = "2.17.0",
+    note = "Drop all references to the ThreadsafeFunction will automatically release it"
+  )]
   pub fn abort(self) -> Result<()> {
     self.handle.with_write_aborted(|mut aborted_guard| {
       if !*aborted_guard {
@@ -416,7 +372,9 @@ impl<T: 'static, ES: ErrorStrategy::T> ThreadsafeFunction<T, ES> {
   }
 }
 
-impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::CalleeHandled> {
+impl<T: 'static, Return: FromNapiValue + 'static, const Weak: bool, const MaxQueueSize: usize>
+  ThreadsafeFunction<T, Return, true, { Weak }, { MaxQueueSize }>
+{
   /// See [napi_call_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_call_threadsafe_function)
   /// for more information.
   pub fn call(&self, value: Result<T>, mode: ThreadsafeFunctionCallMode) -> Status {
@@ -432,7 +390,7 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::CalleeHandled> {
             ThreadsafeFunctionCallJsBackData {
               data,
               call_variant: ThreadsafeFunctionCallVariant::Direct,
-              callback: Box::new(|_d: Result<JsUnknown>| Ok(())),
+              callback: Box::new(|_d: Result<Return>, _| Ok(())),
             }
           })))
           .cast(),
@@ -443,7 +401,8 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::CalleeHandled> {
     })
   }
 
-  pub fn call_with_return_value<D: FromNapiValue, F: 'static + FnOnce(D) -> Result<()>>(
+  /// Call the ThreadsafeFunction, and handle the return value with a callback
+  pub fn call_with_return_value<F: 'static + FnOnce(Result<Return>, Env) -> Result<()>>(
     &self,
     value: Result<T>,
     mode: ThreadsafeFunctionCallMode,
@@ -461,9 +420,7 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::CalleeHandled> {
             ThreadsafeFunctionCallJsBackData {
               data,
               call_variant: ThreadsafeFunctionCallVariant::WithCallback,
-              callback: Box::new(move |d: Result<JsUnknown>| {
-                d.and_then(|d| D::from_napi_value(d.0.env, d.0.value).and_then(cb))
-              }),
+              callback: Box::new(move |d: Result<Return>, env: Env| cb(d, env)),
             }
           })))
           .cast(),
@@ -475,8 +432,9 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::CalleeHandled> {
   }
 
   #[cfg(feature = "tokio_rt")]
-  pub async fn call_async<D: 'static + FromNapiValue>(&self, value: Result<T>) -> Result<D> {
-    let (sender, receiver) = tokio::sync::oneshot::channel::<Result<D>>();
+  /// Call the ThreadsafeFunction, and handle the return value with in `async` way
+  pub async fn call_async(&self, value: Result<T>) -> Result<Return> {
+    let (sender, receiver) = tokio::sync::oneshot::channel::<Result<Return>>();
 
     self.handle.with_read_aborted(|aborted| {
       if aborted {
@@ -491,9 +449,9 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::CalleeHandled> {
               ThreadsafeFunctionCallJsBackData {
                 data,
                 call_variant: ThreadsafeFunctionCallVariant::WithCallback,
-                callback: Box::new(move |d: Result<JsUnknown>| {
+                callback: Box::new(move |d: Result<Return>, _| {
                   sender
-                    .send(d.and_then(|d| D::from_napi_value(d.0.env, d.0.value)))
+                    .send(d)
                     // The only reason for send to return Err is if the receiver isn't listening
                     // Not hiding the error would result in a napi_fatal_error call, it's safe to ignore it instead.
                     .or(Ok(()))
@@ -519,7 +477,9 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::CalleeHandled> {
   }
 }
 
-impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::Fatal> {
+impl<T: 'static, Return: FromNapiValue + 'static, const Weak: bool, const MaxQueueSize: usize>
+  ThreadsafeFunction<T, Return, false, { Weak }, { MaxQueueSize }>
+{
   /// See [napi_call_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_call_threadsafe_function)
   /// for more information.
   pub fn call(&self, value: T, mode: ThreadsafeFunctionCallMode) -> Status {
@@ -534,7 +494,7 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::Fatal> {
           Box::into_raw(Box::new(ThreadsafeFunctionCallJsBackData {
             data: value,
             call_variant: ThreadsafeFunctionCallVariant::Direct,
-            callback: Box::new(|_d: Result<JsUnknown>| Ok(())),
+            callback: Box::new(|_d: Result<Return>, _: Env| Ok(())),
           }))
           .cast(),
           mode.into(),
@@ -544,7 +504,8 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::Fatal> {
     })
   }
 
-  pub fn call_with_return_value<D: FromNapiValue, F: 'static + FnOnce(D) -> Result<()>>(
+  /// Call the ThreadsafeFunction, and handle the return value with a callback
+  pub fn call_with_return_value<F: 'static + FnOnce(Result<Return>, Env) -> Result<()>>(
     &self,
     value: T,
     mode: ThreadsafeFunctionCallMode,
@@ -561,9 +522,7 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::Fatal> {
           Box::into_raw(Box::new(ThreadsafeFunctionCallJsBackData {
             data: value,
             call_variant: ThreadsafeFunctionCallVariant::WithCallback,
-            callback: Box::new(move |d: Result<JsUnknown>| {
-              d.and_then(|d| D::from_napi_value(d.0.env, d.0.value).and_then(cb))
-            }),
+            callback: Box::new(cb),
           }))
           .cast(),
           mode.into(),
@@ -574,8 +533,9 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::Fatal> {
   }
 
   #[cfg(feature = "tokio_rt")]
-  pub async fn call_async<D: 'static + FromNapiValue>(&self, value: T) -> Result<D> {
-    let (sender, receiver) = tokio::sync::oneshot::channel::<D>();
+  /// Call the ThreadsafeFunction, and handle the return value with in `async` way
+  pub async fn call_async(&self, value: T) -> Result<Return> {
+    let (sender, receiver) = tokio::sync::oneshot::channel::<Return>();
 
     self.handle.with_read_aborted(|aborted| {
       if aborted {
@@ -588,15 +548,13 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::Fatal> {
           Box::into_raw(Box::new(ThreadsafeFunctionCallJsBackData {
             data: value,
             call_variant: ThreadsafeFunctionCallVariant::WithCallback,
-            callback: Box::new(move |d: Result<JsUnknown>| {
+            callback: Box::new(move |d, _| {
               d.and_then(|d| {
-                D::from_napi_value(d.0.env, d.0.value).and_then(move |d| {
-                  sender
-                    .send(d)
-                    // The only reason for send to return Err is if the receiver isn't listening
-                    // Not hiding the error would result in a napi_fatal_error call, it's safe to ignore it instead.
-                    .or(Ok(()))
-                })
+                sender
+                  .send(d)
+                  // The only reason for send to return Err is if the receiver isn't listening
+                  // Not hiding the error would result in a napi_fatal_error call, it's safe to ignore it instead.
+                  .or(Ok(()))
               })
             }),
           }))
@@ -612,16 +570,15 @@ impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::Fatal> {
   }
 }
 
-#[allow(unused_variables)]
 unsafe extern "C" fn thread_finalize_cb<T: 'static, V: ToNapiValue, R>(
-  env: sys::napi_env,
+  #[allow(unused_variables)] env: sys::napi_env,
   finalize_data: *mut c_void,
   finalize_hint: *mut c_void,
 ) where
-  R: 'static + Send + FnMut(ThreadSafeCallContext<T>) -> Result<Vec<V>>,
+  R: 'static + Send + FnMut(ThreadsafeCallContext<T>) -> Result<Vec<V>>,
 {
-  let handle_option =
-    unsafe { Weak::from_raw(finalize_data.cast::<ThreadsafeFunctionHandle>()).upgrade() };
+  let handle_option: Option<Arc<ThreadsafeFunctionHandle>> =
+    unsafe { sync::Weak::from_raw(finalize_data.cast()).upgrade() };
 
   if let Some(handle) = handle_option {
     handle.with_write_aborted(|mut aborted_guard| {
@@ -635,29 +592,31 @@ unsafe extern "C" fn thread_finalize_cb<T: 'static, V: ToNapiValue, R>(
   drop(unsafe { Box::<R>::from_raw(finalize_hint.cast()) });
 }
 
-unsafe extern "C" fn call_js_cb<T: 'static, V: ToNapiValue, R, ES>(
+unsafe extern "C" fn call_js_cb<
+  T: 'static,
+  Return: FromNapiValue,
+  V: ToNapiValue,
+  R,
+  const CalleeHandled: bool,
+>(
   raw_env: sys::napi_env,
   js_callback: sys::napi_value,
   context: *mut c_void,
   data: *mut c_void,
 ) where
-  R: 'static + Send + FnMut(ThreadSafeCallContext<T>) -> Result<Vec<V>>,
-  ES: ErrorStrategy::T,
+  R: 'static + Send + FnMut(ThreadsafeCallContext<T>) -> Result<Vec<V>>,
 {
   // env and/or callback can be null when shutting down
   if raw_env.is_null() || js_callback.is_null() {
     return;
   }
 
-  let ctx: &mut R = unsafe { Box::leak(Box::from_raw(context.cast())) };
+  let callback: &mut R = unsafe { Box::leak(Box::from_raw(context.cast())) };
   let val = unsafe {
-    match ES::VALUE {
-      ErrorStrategy::CalleeHandled::VALUE => {
-        *Box::<Result<ThreadsafeFunctionCallJsBackData<T>>>::from_raw(data.cast())
-      }
-      ErrorStrategy::Fatal::VALUE => Ok(*Box::<ThreadsafeFunctionCallJsBackData<T>>::from_raw(
-        data.cast(),
-      )),
+    if CalleeHandled {
+      *Box::<Result<ThreadsafeFunctionCallJsBackData<T, Return>>>::from_raw(data.cast())
+    } else {
+      Ok(*Box::<ThreadsafeFunctionCallJsBackData<T, Return>>::from_raw(data.cast()))
     }
   };
 
@@ -665,8 +624,8 @@ unsafe extern "C" fn call_js_cb<T: 'static, V: ToNapiValue, R, ES>(
   unsafe { sys::napi_get_undefined(raw_env, &mut recv) };
 
   let ret = val.and_then(|v| {
-    (ctx)(ThreadSafeCallContext {
-      env: unsafe { Env::from_raw(raw_env) },
+    (callback)(ThreadsafeCallContext {
+      env: Env::from_raw(raw_env),
       value: v.data,
     })
     .map(|ret| (ret, v.call_variant, v.callback))
@@ -680,7 +639,7 @@ unsafe extern "C" fn call_js_cb<T: 'static, V: ToNapiValue, R, ES>(
       let values = values
         .into_iter()
         .map(|v| unsafe { ToNapiValue::to_napi_value(raw_env, v) });
-      let args: Result<Vec<sys::napi_value>> = if ES::VALUE == ErrorStrategy::CalleeHandled::VALUE {
+      let args: Result<Vec<sys::napi_value>> = if CalleeHandled {
         let mut js_null = ptr::null_mut();
         unsafe { sys::napi_get_null(raw_env, &mut js_null) };
         ::core::iter::once(Ok(js_null)).chain(values).collect()
@@ -699,62 +658,45 @@ unsafe extern "C" fn call_js_cb<T: 'static, V: ToNapiValue, R, ES>(
             &mut return_value,
           )
         },
-        Err(e) => match ES::VALUE {
-          ErrorStrategy::Fatal::VALUE => unsafe {
-            sys::napi_fatal_exception(raw_env, JsError::from(e).into_value(raw_env))
-          },
-          ErrorStrategy::CalleeHandled::VALUE => unsafe {
-            sys::napi_call_function(
-              raw_env,
-              recv,
-              js_callback,
-              1,
-              [JsError::from(e).into_value(raw_env)].as_mut_ptr(),
-              &mut return_value,
-            )
-          },
-        },
+        Err(e) => {
+          if CalleeHandled {
+            unsafe { sys::napi_fatal_exception(raw_env, JsError::from(e).into_value(raw_env)) }
+          } else {
+            unsafe {
+              sys::napi_call_function(
+                raw_env,
+                recv,
+                js_callback,
+                1,
+                [JsError::from(e).into_value(raw_env)].as_mut_ptr(),
+                &mut return_value,
+              )
+            }
+          }
+        }
       };
       if let ThreadsafeFunctionCallVariant::WithCallback = call_variant {
         // throw Error in JavaScript callback
         let callback_arg = if status == sys::Status::napi_pending_exception {
           let mut exception = ptr::null_mut();
           status = unsafe { sys::napi_get_and_clear_last_exception(raw_env, &mut exception) };
-          Err(
-            JsUnknown(crate::Value {
-              env: raw_env,
-              value: exception,
-              value_type: crate::ValueType::Unknown,
-            })
-            .into(),
-          )
+          let mut error_reference = ptr::null_mut();
+          unsafe { sys::napi_create_reference(raw_env, exception, 1, &mut error_reference) };
+          Err(Error {
+            maybe_raw: error_reference,
+            status: Status::from(status),
+            reason: "".to_owned(),
+          })
         } else {
-          Ok(JsUnknown(crate::Value {
-            env: raw_env,
-            value: return_value,
-            value_type: crate::ValueType::Unknown,
-          }))
+          unsafe { Return::from_napi_value(raw_env, return_value) }
         };
-        if let Err(err) = callback(callback_arg) {
-          let message = format!(
-            "Failed to convert return value in ThreadsafeFunction callback into Rust value: {}",
-            err
-          );
-          let message_length = message.len();
-          let c_message = CString::new(message).unwrap();
-          unsafe {
-            sys::napi_fatal_error(
-              "threadsafe_function.rs:749\0".as_ptr().cast(),
-              26,
-              c_message.as_ptr(),
-              message_length,
-            )
-          };
+        if let Err(err) = callback(callback_arg, Env::from_raw(raw_env)) {
+          unsafe { sys::napi_fatal_exception(raw_env, JsError::from(err).into_value(raw_env)) };
         }
       }
       status
     }
-    Err(e) if ES::VALUE == ErrorStrategy::Fatal::VALUE => unsafe {
+    Err(e) if !CalleeHandled => unsafe {
       sys::napi_fatal_exception(raw_env, JsError::from(e).into_value(raw_env))
     },
     Err(e) => unsafe {
@@ -783,27 +725,27 @@ unsafe extern "C" fn call_js_cb<T: 'static, V: ToNapiValue, R, ES>(
     assert!(stat == sys::Status::napi_ok || stat == sys::Status::napi_pending_exception);
   } else {
     let error_code: Status = status.into();
-    let error_code_string = format!("{:?}", error_code);
+    let error_code_string = format!("{}", error_code);
     let mut error_code_value = ptr::null_mut();
     assert_eq!(
       unsafe {
         sys::napi_create_string_utf8(
           raw_env,
-          error_code_string.as_ptr() as *const _,
+          error_code_string.as_ptr().cast(),
           error_code_string.len(),
           &mut error_code_value,
         )
       },
       sys::Status::napi_ok,
     );
-    let error_msg = "Call JavaScript callback failed in threadsafe function";
+    static ERROR_MSG: &str = "Call JavaScript callback failed in threadsafe function";
     let mut error_msg_value = ptr::null_mut();
     assert_eq!(
       unsafe {
         sys::napi_create_string_utf8(
           raw_env,
-          error_msg.as_ptr() as *const _,
-          error_msg.len(),
+          ERROR_MSG.as_ptr().cast(),
+          ERROR_MSG.len(),
           &mut error_msg_value,
         )
       },
@@ -823,99 +765,6 @@ unsafe extern "C" fn call_js_cb<T: 'static, V: ToNapiValue, R, ES>(
   }
 }
 
-/// Helper
-macro_rules! type_level_enum {(
-  $( #[doc = $doc:tt] )*
-  $pub:vis
-  enum $EnumName:ident {
-    $(
-      $( #[doc = $doc_variant:tt] )*
-      $Variant:ident
-    ),* $(,)?
-  }
-) => (type_level_enum! { // This requires the macro to be in scope when called.
-  with_docs! {
-    $( #[doc = $doc] )*
-    ///
-    /// ### Type-level `enum`
-    ///
-    /// Until `const_generics` can handle custom `enum`s, this pattern must be
-    /// implemented at the type level.
-    ///
-    /// We thus end up with:
-    ///
-    /// ```rust,ignore
-    /// #[type_level_enum]
-    #[doc = ::core::concat!(
-      " enum ", ::core::stringify!($EnumName), " {",
-    )]
-    $(
-      #[doc = ::core::concat!(
-        "     ", ::core::stringify!($Variant), ",",
-      )]
-    )*
-    #[doc = " }"]
-    /// ```
-    ///
-    #[doc = ::core::concat!(
-      "With [`", ::core::stringify!($EnumName), "::T`](#reexports) \
-      being the type-level \"enum type\":",
-    )]
-    ///
-    /// ```rust,ignore
-    #[doc = ::core::concat!(
-      "<Param: ", ::core::stringify!($EnumName), "::T>"
-    )]
-    /// ```
-  }
-  #[allow(warnings)]
-  $pub mod $EnumName {
-    #[doc(no_inline)]
-    pub use $EnumName as T;
-
-    super::type_level_enum! {
-      with_docs! {
-        #[doc = ::core::concat!(
-          "See [`", ::core::stringify!($EnumName), "`]\
-          [super::", ::core::stringify!($EnumName), "]"
-        )]
-      }
-      pub trait $EnumName : __sealed::$EnumName + ::core::marker::Sized + 'static {
-        const VALUE: __value::$EnumName;
-      }
-    }
-
-    mod __sealed { pub trait $EnumName {} }
-
-    mod __value {
-      #[derive(Debug, PartialEq, Eq)]
-      pub enum $EnumName { $( $Variant ),* }
-    }
-
-    $(
-      $( #[doc = $doc_variant] )*
-      pub enum $Variant {}
-      impl __sealed::$EnumName for $Variant {}
-      impl $EnumName for $Variant {
-        const VALUE: __value::$EnumName = __value::$EnumName::$Variant;
-      }
-      impl $Variant {
-        pub const VALUE: __value::$EnumName = __value::$EnumName::$Variant;
-      }
-    )*
-  }
-});(
-  with_docs! {
-    $( #[doc = $doc:expr] )*
-  }
-  $item:item
-) => (
-  $( #[doc = $doc] )*
-  $item
-)}
-
-use type_level_enum;
-
 pub struct UnknownReturnValue;
 
 impl TypeName for UnknownReturnValue {
diff --git a/examples/napi-compat-mode/__tests__/function.spec.ts b/examples/napi-compat-mode/__tests__/function.spec.ts
index 0c8e30a5..d1546ec4 100644
--- a/examples/napi-compat-mode/__tests__/function.spec.ts
+++ b/examples/napi-compat-mode/__tests__/function.spec.ts
@@ -36,7 +36,7 @@ test('should be able to create function from closure', (t) => {
   for (let i = 0; i < 100; i++) {
     t.is(
       bindings.testCreateFunctionFromClosure()(
-        ...Array.from({ length: i }).map((_, i) => i),
+        ...Array.from({ length: i }, (_, i) => i),
       ),
       `arguments length: ${i}`,
     )
diff --git a/examples/napi-compat-mode/src/class.rs b/examples/napi-compat-mode/src/class.rs
index 7a2460b5..484f31f0 100644
--- a/examples/napi-compat-mode/src/class.rs
+++ b/examples/napi-compat-mode/src/class.rs
@@ -1,13 +1,16 @@
 use std::convert::TryInto;
 
-use napi::{CallContext, JsFunction, JsNumber, JsObject, JsUndefined, Property, Result};
+use napi::{
+  bindgen_prelude::{Function, Unknown},
+  CallContext, JsNumber, JsObject, JsUndefined, Property, Result,
+};
 
 struct NativeClass {
   value: i32,
 }
 
 #[js_function(1)]
-fn create_test_class(ctx: CallContext) -> Result<JsFunction> {
+fn create_test_class(ctx: CallContext) -> Result<Function<Unknown, Unknown>> {
   let add_count_method = Property::new("addCount")?.with_method(add_count);
   let add_native_count = Property::new("addNativeCount")?.with_method(add_native_count);
   let renew_wrapped = Property::new("renewWrapped")?.with_method(renew_wrapped);
@@ -56,7 +59,7 @@ fn renew_wrapped(ctx: CallContext) -> Result<JsUndefined> {
 }
 
 #[js_function(1)]
-fn new_test_class(ctx: CallContext) -> Result<JsObject> {
+fn new_test_class(ctx: CallContext) -> Result<Unknown> {
   let add_count_method = Property::new("addCount")?.with_method(add_count);
   let add_native_count = Property::new("addNativeCount")?.with_method(add_native_count);
   let properties = vec![add_count_method, add_native_count];
@@ -65,7 +68,7 @@ fn new_test_class(ctx: CallContext) -> Result<JsObject> {
       .env
       .define_class("TestClass", test_class_constructor, properties.as_slice())?;
 
-  test_class.new_instance(&[ctx.env.create_int32(42)?])
+  test_class.new_instance(42)
 }
 
 pub fn register_js(exports: &mut JsObject) -> Result<()> {
diff --git a/examples/napi-compat-mode/src/function.rs b/examples/napi-compat-mode/src/function.rs
index c51bc9f5..6e62e0b8 100644
--- a/examples/napi-compat-mode/src/function.rs
+++ b/examples/napi-compat-mode/src/function.rs
@@ -1,4 +1,6 @@
-use napi::{CallContext, JsError, JsFunction, JsNull, JsObject, JsUnknown, Result};
+use napi::{
+  bindgen_prelude::Function, CallContext, JsError, JsFunction, JsNull, JsObject, JsUnknown, Result,
+};
 
 #[js_function(1)]
 pub fn call_function(ctx: CallContext) -> Result<JsNull> {
@@ -44,15 +46,16 @@ pub fn call_function_error(ctx: CallContext) -> Result<JsUnknown> {
 }
 
 #[js_function(0)]
-pub fn test_create_function_from_closure(ctx: CallContext) -> Result<JsFunction> {
+pub fn test_create_function_from_closure(ctx: CallContext) -> Result<Function<u32, String>> {
   ctx
     .env
     .create_function_from_closure("functionFromClosure", move |ctx| {
-      if ctx.length != 0 {
-        let max: u32 = ctx.get(ctx.length - 1)?;
-        assert_eq!(max, ctx.length as u32 - 1);
+      if ctx.length() != 0 {
+        let args = ctx.arguments::<u32>()?;
+        let max = args.last().unwrap();
+        assert_eq!(*max, ctx.length() as u32 - 1);
       }
-      Ok(format!("arguments length: {}", ctx.length))
+      Ok(format!("arguments length: {}", ctx.length()))
     })
 }
 
diff --git a/examples/napi-compat-mode/src/global.rs b/examples/napi-compat-mode/src/global.rs
index 6dcff50d..b4443ba6 100644
--- a/examples/napi-compat-mode/src/global.rs
+++ b/examples/napi-compat-mode/src/global.rs
@@ -1,10 +1,10 @@
 use std::convert::TryInto;
 
-use napi::{CallContext, JsFunction, JsNumber, JsObject, JsTimeout, JsUndefined, Result};
+use napi::{CallContext, JsNumber, JsObject, JsTimeout, JsUndefined, Result};
 
 #[js_function(2)]
 pub fn set_timeout(ctx: CallContext) -> Result<JsTimeout> {
-  let handler: JsFunction = ctx.get(0)?;
+  let handler = ctx.get(0)?;
   let timeout: JsNumber = ctx.get(1)?;
   ctx
     .env
diff --git a/examples/napi-compat-mode/src/lib.rs b/examples/napi-compat-mode/src/lib.rs
index 74c89192..d0d5b220 100644
--- a/examples/napi-compat-mode/src/lib.rs
+++ b/examples/napi-compat-mode/src/lib.rs
@@ -1,5 +1,6 @@
 #![allow(unused_variables)]
 #![allow(clippy::uninlined_format_args)]
+#![allow(deprecated)]
 
 #[macro_use]
 extern crate napi_derive;
diff --git a/examples/napi-compat-mode/src/napi4/mod.rs b/examples/napi-compat-mode/src/napi4/mod.rs
index 27b375d1..33c1840f 100644
--- a/examples/napi-compat-mode/src/napi4/mod.rs
+++ b/examples/napi-compat-mode/src/napi4/mod.rs
@@ -1,4 +1,4 @@
-use napi::{Env, JsObject, Property, Result};
+use napi::{bindgen_prelude::Unknown, Env, JsObject, Property, Result};
 
 mod deferred;
 mod tsfn;
@@ -26,7 +26,7 @@ pub fn register_js(exports: &mut JsObject, env: &Env) -> Result<()> {
   exports.create_named_method("testTsfnWithRef", test_tsfn_with_ref)?;
   exports.create_named_method("testDeferred", deferred::test_deferred)?;
 
-  let obj = env.define_class(
+  let obj = env.define_class::<Unknown>(
     "A",
     constructor,
     &[
diff --git a/examples/napi/__tests__/__snapshots__/typegen.spec.ts.md b/examples/napi/__tests__/__snapshots__/typegen.spec.ts.md
index d6b71e9a..3b9bd06e 100644
--- a/examples/napi/__tests__/__snapshots__/typegen.spec.ts.md
+++ b/examples/napi/__tests__/__snapshots__/typegen.spec.ts.md
@@ -251,7 +251,7 @@ Generated by [AVA](https://avajs.dev).
     ␊
     export function acceptThreadsafeFunction(func: (err: Error | null, arg: number) => any): void␊
     ␊
-    export function acceptThreadsafeFunctionFatal(func: (arg: number) => any): void␊
+    export function acceptThreadsafeFunctionFatal(func: (arg: number) => void): void␊
     ␊
     export function acceptThreadsafeFunctionTupleArgs(func: (err: Error | null, arg0: number, arg1: boolean, arg2: string) => any): void␊
     ␊
@@ -310,6 +310,8 @@ Generated by [AVA](https://avajs.dev).
     ␊
     export function bufferPassThrough(buf: Buffer): Promise<Buffer>␊
     ␊
+    export function buildThreadsafeFunctionFromFunction(callback: (arg0: number, arg1: number) => number): void␊
+    ␊
     export interface C {␊
       baz: number␊
     }␊
@@ -330,9 +332,9 @@ Generated by [AVA](https://avajs.dev).
     ␊
     export function callFunctionWithArgAndCtx(ctx: Animal, cb: (arg: string) => void, name: string): void␊
     ␊
-    export function callLongThreadsafeFunction(callback: (...args: any[]) => any): void␊
+    export function callLongThreadsafeFunction(tsfn: (err: Error | null, arg: number) => unknown): void␊
     ␊
-    export function callThreadsafeFunction(callback: (...args: any[]) => any): void␊
+    export function callThreadsafeFunction(tsfn: (err: Error | null, arg: number) => unknown): void␊
     ␊
     export function captureErrorInCallback(cb1: () => void, cb2: (arg0: Error) => void): void␊
     ␊
@@ -639,11 +641,11 @@ Generated by [AVA](https://avajs.dev).
     ␊
     export function threadsafeFunctionClosureCapture(func: (...args: any[]) => any): void␊
     ␊
-    export function threadsafeFunctionFatalMode(cb: (...args: any[]) => any): void␊
+    export function threadsafeFunctionFatalMode(cb: (arg: boolean) => unknown): void␊
     ␊
-    export function threadsafeFunctionFatalModeError(cb: (...args: any[]) => any): void␊
+    export function threadsafeFunctionFatalModeError(cb: (arg: boolean) => string): void␊
     ␊
-    export function threadsafeFunctionThrowError(cb: (...args: any[]) => any): void␊
+    export function threadsafeFunctionThrowError(cb: (err: Error | null, arg: boolean) => unknown): void␊
     ␊
     export function throwAsyncError(): Promise<void>␊
     ␊
@@ -653,15 +655,15 @@ Generated by [AVA](https://avajs.dev).
     ␊
     export function toJsObj(): object␊
     ␊
-    export function tsfnAsyncCall(func: (...args: any[]) => any): Promise<void>␊
+    export function tsfnAsyncCall(func: (arg0: number, arg1: number, arg2: number) => string): Promise<void>␊
     ␊
-    export function tsfnCallWithCallback(func: (...args: any[]) => any): void␊
+    export function tsfnCallWithCallback(tsfn: (err: Error | null, ) => string): void␊
     ␊
-    export function tsfnReturnPromise(func: (err: Error | null, arg: number) => any): Promise<number>␊
+    export function tsfnReturnPromise(func: (err: Error | null, arg: number) => Promise<number>): Promise<number>␊
     ␊
-    export function tsfnReturnPromiseTimeout(func: (err: Error | null, arg: number) => any): Promise<number>␊
+    export function tsfnReturnPromiseTimeout(func: (err: Error | null, arg: number) => Promise<number>): Promise<number>␊
     ␊
-    export function tsfnThrowFromJs(tsfn: (err: Error | null, arg: number) => any): Promise<number>␊
+    export function tsfnThrowFromJs(tsfn: (err: Error | null, arg: number) => Promise<number>): Promise<number>␊
     ␊
     export function tsRename(a: { foo: number }): string[]␊
     ␊
diff --git a/examples/napi/__tests__/__snapshots__/typegen.spec.ts.snap b/examples/napi/__tests__/__snapshots__/typegen.spec.ts.snap
index ab45356b..1a6b9320 100644
Binary files a/examples/napi/__tests__/__snapshots__/typegen.spec.ts.snap and b/examples/napi/__tests__/__snapshots__/typegen.spec.ts.snap differ
diff --git a/examples/napi/__tests__/__snapshots__/values.spec.ts.md b/examples/napi/__tests__/__snapshots__/values.spec.ts.md
index 8a3e6fe6..5c0cacb5 100644
--- a/examples/napi/__tests__/__snapshots__/values.spec.ts.md
+++ b/examples/napi/__tests__/__snapshots__/values.spec.ts.md
@@ -19,6 +19,7 @@ Generated by [AVA](https://avajs.dev).
       'cross-env',
       'electron',
       'lodash',
+      'rxjs',
       'sinon',
       'vite',
       'vite-plugin-node-polyfills',
diff --git a/examples/napi/__tests__/__snapshots__/values.spec.ts.snap b/examples/napi/__tests__/__snapshots__/values.spec.ts.snap
index d4241d4d..2b1be196 100644
Binary files a/examples/napi/__tests__/__snapshots__/values.spec.ts.snap and b/examples/napi/__tests__/__snapshots__/values.spec.ts.snap differ
diff --git a/examples/napi/__tests__/tsfn-error.cjs b/examples/napi/__tests__/tsfn-error.cjs
index 6007bfa1..aecafb21 100644
--- a/examples/napi/__tests__/tsfn-error.cjs
+++ b/examples/napi/__tests__/tsfn-error.cjs
@@ -1,5 +1,5 @@
-import('../index.cjs').then(
-  ({ threadsafeFunctionFatalModeError }) => {
-    return threadsafeFunctionFatalModeError(() => {})
-  },
-)
+const { threadsafeFunctionFatalModeError } = require('../index.cjs')
+
+threadsafeFunctionFatalModeError(() => {
+  return false
+})
diff --git a/examples/napi/__tests__/values.spec.ts b/examples/napi/__tests__/values.spec.ts
index 76e68131..d10a9244 100644
--- a/examples/napi/__tests__/values.spec.ts
+++ b/examples/napi/__tests__/values.spec.ts
@@ -2,6 +2,7 @@ import { exec } from 'node:child_process'
 import { join } from 'node:path'
 import { fileURLToPath } from 'node:url'
 
+import { Subject, take } from 'rxjs'
 import { spy } from 'sinon'
 
 import {
@@ -170,6 +171,7 @@ import {
   throwSyntaxError,
   type AliasedStruct,
   returnObjectOnlyToJs,
+  buildThreadsafeFunctionFromFunction,
 } from '../index.cjs'
 
 import { test } from './test.framework.js'
@@ -968,7 +970,7 @@ BigIntTest('from i128 i64', (t) => {
   t.is(bigintFromI128(), BigInt('-100'))
 })
 
-Napi4Test('call thread safe function', (t) => {
+Napi4Test('call ThreadsafeFunction', (t) => {
   let i = 0
   let value = 0
   return new Promise((resolve) => {
@@ -980,14 +982,14 @@ Napi4Test('call thread safe function', (t) => {
         resolve()
         t.is(
           value,
-          Array.from({ length: 100 }, (_, i) => i + 1).reduce((a, b) => a + b),
+          Array.from({ length: 100 }, (_, i) => i).reduce((a, b) => a + b),
         )
       }
     })
   })
 })
 
-Napi4Test('throw error from thread safe function', async (t) => {
+Napi4Test('throw error from ThreadsafeFunction', async (t) => {
   const throwPromise = new Promise((_, reject) => {
     threadsafeFunctionThrowError(reject)
   })
@@ -995,7 +997,7 @@ Napi4Test('throw error from thread safe function', async (t) => {
   t.is(err?.message, 'ThrowFromNative')
 })
 
-Napi4Test('thread safe function closure capture data', (t) => {
+Napi4Test('ThreadsafeFunction closure capture data', (t) => {
   return new Promise((resolve) => {
     threadsafeFunctionClosureCapture(() => {
       resolve()
@@ -1024,7 +1026,7 @@ Napi4Test('throw error from thread safe function fatal mode', (t) => {
       t.is(code, 1)
       const stderrMsg = stderr.toString('utf8')
       console.info(stderrMsg)
-      t.true(stderrMsg.includes(`Error: Generic tsfn error`))
+      t.true(stderrMsg.includes(`Error: Failed to convert JavaScript value`))
       resolve()
     })
   })
@@ -1060,8 +1062,7 @@ Napi4Test('call ThreadsafeFunction with callback', async (t) => {
 
 Napi4Test('async call ThreadsafeFunction', async (t) => {
   await t.notThrowsAsync(() =>
-    tsfnAsyncCall((err, arg1, arg2, arg3) => {
-      t.is(err, null)
+    tsfnAsyncCall((arg1, arg2, arg3) => {
       t.is(arg1, 0)
       t.is(arg2, 1)
       t.is(arg3, 2)
@@ -1163,6 +1164,20 @@ Napi4Test('object only from js', (t) => {
   })
 })
 
+Napi4Test('build ThreadsafeFunction from Function', (t) => {
+  const subject = new Subject<void>()
+  const fn = (a: number, b: number) => {
+    t.is(a, 1)
+    t.is(b, 2)
+    subject.next()
+    return a * b
+  }
+
+  buildThreadsafeFunctionFromFunction(fn)
+
+  return subject.pipe(take(3))
+})
+
 Napi4Test('promise in either', async (t) => {
   t.is(await promiseInEither(1), false)
   t.is(await promiseInEither(20), true)
diff --git a/examples/napi/electron.cjs b/examples/napi/electron.cjs
index 0d35c543..4f7c9952 100644
--- a/examples/napi/electron.cjs
+++ b/examples/napi/electron.cjs
@@ -85,7 +85,7 @@ async function main() {
 
   assert(
     value ===
-      Array.from({ length: 100 }, (_, i) => i + 1).reduce((a, b) => a + b),
+      Array.from({ length: 100 }, (_, i) => i).reduce((a, b) => a + b),
   )
   console.info(createExternalTypedArray())
 }
diff --git a/examples/napi/index.cjs b/examples/napi/index.cjs
index eb2b6fb3..2cf9a4bd 100644
--- a/examples/napi/index.cjs
+++ b/examples/napi/index.cjs
@@ -398,6 +398,7 @@ module.exports.bigintFromI128 = nativeBinding.bigintFromI128
 module.exports.bigintFromI64 = nativeBinding.bigintFromI64
 module.exports.bigintGetU64AsString = nativeBinding.bigintGetU64AsString
 module.exports.bufferPassThrough = nativeBinding.bufferPassThrough
+module.exports.buildThreadsafeFunctionFromFunction = nativeBinding.buildThreadsafeFunctionFromFunction
 module.exports.call0 = nativeBinding.call0
 module.exports.call1 = nativeBinding.call1
 module.exports.call2 = nativeBinding.call2
diff --git a/examples/napi/index.d.cts b/examples/napi/index.d.cts
index 19f89483..b4959e23 100644
--- a/examples/napi/index.d.cts
+++ b/examples/napi/index.d.cts
@@ -241,7 +241,7 @@ export function acceptSlice(fixture: Uint8Array): bigint
 
 export function acceptThreadsafeFunction(func: (err: Error | null, arg: number) => any): void
 
-export function acceptThreadsafeFunctionFatal(func: (arg: number) => any): void
+export function acceptThreadsafeFunctionFatal(func: (arg: number) => void): void
 
 export function acceptThreadsafeFunctionTupleArgs(func: (err: Error | null, arg0: number, arg1: boolean, arg2: string) => any): void
 
@@ -300,6 +300,8 @@ export function bigintGetU64AsString(bi: bigint): string
 
 export function bufferPassThrough(buf: Buffer): Promise<Buffer>
 
+export function buildThreadsafeFunctionFromFunction(callback: (arg0: number, arg1: number) => number): void
+
 export interface C {
   baz: number
 }
@@ -320,9 +322,9 @@ export function callFunctionWithArg(cb: (arg0: number, arg1: number) => number,
 
 export function callFunctionWithArgAndCtx(ctx: Animal, cb: (arg: string) => void, name: string): void
 
-export function callLongThreadsafeFunction(callback: (...args: any[]) => any): void
+export function callLongThreadsafeFunction(tsfn: (err: Error | null, arg: number) => unknown): void
 
-export function callThreadsafeFunction(callback: (...args: any[]) => any): void
+export function callThreadsafeFunction(tsfn: (err: Error | null, arg: number) => unknown): void
 
 export function captureErrorInCallback(cb1: () => void, cb2: (arg0: Error) => void): void
 
@@ -629,11 +631,11 @@ export function testSerdeRoundtrip(data: any): any
 
 export function threadsafeFunctionClosureCapture(func: (...args: any[]) => any): void
 
-export function threadsafeFunctionFatalMode(cb: (...args: any[]) => any): void
+export function threadsafeFunctionFatalMode(cb: (arg: boolean) => unknown): void
 
-export function threadsafeFunctionFatalModeError(cb: (...args: any[]) => any): void
+export function threadsafeFunctionFatalModeError(cb: (arg: boolean) => string): void
 
-export function threadsafeFunctionThrowError(cb: (...args: any[]) => any): void
+export function threadsafeFunctionThrowError(cb: (err: Error | null, arg: boolean) => unknown): void
 
 export function throwAsyncError(): Promise<void>
 
@@ -643,15 +645,15 @@ export function throwSyntaxError(error: string, code?: string | undefined | null
 
 export function toJsObj(): object
 
-export function tsfnAsyncCall(func: (...args: any[]) => any): Promise<void>
+export function tsfnAsyncCall(func: (arg0: number, arg1: number, arg2: number) => string): Promise<void>
 
-export function tsfnCallWithCallback(func: (...args: any[]) => any): void
+export function tsfnCallWithCallback(tsfn: (err: Error | null, ) => string): void
 
-export function tsfnReturnPromise(func: (err: Error | null, arg: number) => any): Promise<number>
+export function tsfnReturnPromise(func: (err: Error | null, arg: number) => Promise<number>): Promise<number>
 
-export function tsfnReturnPromiseTimeout(func: (err: Error | null, arg: number) => any): Promise<number>
+export function tsfnReturnPromiseTimeout(func: (err: Error | null, arg: number) => Promise<number>): Promise<number>
 
-export function tsfnThrowFromJs(tsfn: (err: Error | null, arg: number) => any): Promise<number>
+export function tsfnThrowFromJs(tsfn: (err: Error | null, arg: number) => Promise<number>): Promise<number>
 
 export function tsRename(a: { foo: number }): string[]
 
diff --git a/examples/napi/package.json b/examples/napi/package.json
index 098f9a69..acc66a10 100644
--- a/examples/napi/package.json
+++ b/examples/napi/package.json
@@ -24,6 +24,7 @@
     "cross-env": "7.0.3",
     "electron": "^29.0.1",
     "lodash": "^4.17.21",
+    "rxjs": "^7.8.1",
     "sinon": "^17.0.1",
     "vite": "^5.0.12",
     "vite-plugin-node-polyfills": "^0.19.0",
diff --git a/examples/napi/src/callback.rs b/examples/napi/src/callback.rs
index 87156629..86f1d1dd 100644
--- a/examples/napi/src/callback.rs
+++ b/examples/napi/src/callback.rs
@@ -2,7 +2,7 @@ use std::{env, format};
 
 use napi::{
   bindgen_prelude::*,
-  threadsafe_function::{ThreadSafeCallContext, ThreadsafeFunction, ThreadsafeFunctionCallMode},
+  threadsafe_function::{ThreadsafeCallContext, ThreadsafeFunction, ThreadsafeFunctionCallMode},
   JsUnknown,
 };
 
@@ -65,7 +65,7 @@ fn callback_return_promise<T: Fn() -> Result<JsUnknown>>(
   if ret.is_promise()? {
     let p = Promise::<String>::from_unknown(ret)?;
     let fn_out_tsfn: ThreadsafeFunction<String> = fn_out
-      .create_threadsafe_function(0, |ctx: ThreadSafeCallContext<String>| Ok(vec![ctx.value]))?;
+      .create_threadsafe_function(|ctx: ThreadsafeCallContext<String>| Ok(vec![ctx.value]))?;
     env
       .execute_tokio_future(
         async move {
diff --git a/examples/napi/src/date.rs b/examples/napi/src/date.rs
index 584e6d15..e0566d2e 100644
--- a/examples/napi/src/date.rs
+++ b/examples/napi/src/date.rs
@@ -15,7 +15,7 @@ fn chrono_date_to_millis(input: chrono::DateTime<Utc>) -> i64 {
 
 #[napi]
 fn chrono_date_add_1_minute(input: chrono::DateTime<Utc>) -> chrono::DateTime<Utc> {
-  input + Duration::minutes(1)
+  Duration::try_minutes(1).map(|d| input + d).unwrap()
 }
 
 #[napi(object)]
@@ -26,7 +26,7 @@ pub struct Dates {
 
 #[napi]
 pub fn chrono_native_date_time(date: chrono::NaiveDateTime) -> i64 {
-  date.timestamp_millis()
+  date.and_utc().timestamp_millis()
 }
 
 #[napi]
diff --git a/examples/napi/src/enum.rs b/examples/napi/src/enum.rs
index 7192662a..444f4065 100644
--- a/examples/napi/src/enum.rs
+++ b/examples/napi/src/enum.rs
@@ -19,6 +19,7 @@ pub enum Status {
   Ready,
 }
 
+#[allow(clippy::enum_variant_names)]
 #[napi(string_enum = "lowercase")]
 pub enum StringEnum {
   VariantOne,
diff --git a/examples/napi/src/function.rs b/examples/napi/src/function.rs
index f456a425..737c5836 100644
--- a/examples/napi/src/function.rs
+++ b/examples/napi/src/function.rs
@@ -1,5 +1,8 @@
+#![allow(deprecated)]
+
 use napi::{
   bindgen_prelude::{ClassInstance, Function, FunctionRef},
+  threadsafe_function::ThreadsafeFunctionCallMode,
   Env, JsFunction, JsObject, Result,
 };
 
@@ -74,3 +77,30 @@ pub fn reference_as_callback(
 ) -> Result<u32> {
   callback.borrow_back(&env)?.call((arg0, arg1))
 }
+
+#[napi]
+pub fn build_threadsafe_function_from_function(callback: Function<(u32, u32), u32>) -> Result<()> {
+  let tsfn = callback.build_threadsafe_function().build()?;
+  std::thread::spawn(move || {
+    tsfn.call((1, 2), ThreadsafeFunctionCallMode::NonBlocking);
+  });
+  let tsfn_max_queue_size_1 = callback
+    .build_threadsafe_function()
+    .max_queue_size::<1>()
+    .build()?;
+
+  std::thread::spawn(move || {
+    tsfn_max_queue_size_1.call((1, 2), ThreadsafeFunctionCallMode::NonBlocking);
+  });
+
+  let tsfn_weak = callback
+    .build_threadsafe_function()
+    .weak::<true>()
+    .build()?;
+
+  std::thread::spawn(move || {
+    tsfn_weak.call((1, 2), ThreadsafeFunctionCallMode::NonBlocking);
+  });
+
+  Ok(())
+}
diff --git a/examples/napi/src/lib.rs b/examples/napi/src/lib.rs
index b5192452..4d8f0133 100644
--- a/examples/napi/src/lib.rs
+++ b/examples/napi/src/lib.rs
@@ -3,6 +3,7 @@
 #![allow(clippy::disallowed_names)]
 #![allow(clippy::uninlined_format_args)]
 #![allow(clippy::new_without_default)]
+#![allow(deprecated)]
 
 #[macro_use]
 extern crate napi_derive;
diff --git a/examples/napi/src/threadsafe_function.rs b/examples/napi/src/threadsafe_function.rs
index 0bbeb2c6..a3238358 100644
--- a/examples/napi/src/threadsafe_function.rs
+++ b/examples/napi/src/threadsafe_function.rs
@@ -2,14 +2,12 @@ use std::{thread, time::Duration};
 
 use napi::{
   bindgen_prelude::*,
-  threadsafe_function::{ErrorStrategy, ThreadsafeFunction, ThreadsafeFunctionCallMode},
-  JsBoolean, JsString,
+  threadsafe_function::{ThreadsafeFunction, ThreadsafeFunctionCallMode, UnknownReturnValue},
+  JsString,
 };
 
 #[napi]
-pub fn call_threadsafe_function(callback: JsFunction) -> Result<()> {
-  let tsfn: ThreadsafeFunction<u32, ErrorStrategy::CalleeHandled> =
-    callback.create_threadsafe_function(0, |ctx| Ok(vec![ctx.value + 1]))?;
+pub fn call_threadsafe_function(tsfn: ThreadsafeFunction<u32, UnknownReturnValue>) -> Result<()> {
   for n in 0..100 {
     let tsfn = tsfn.clone();
     thread::spawn(move || {
@@ -20,9 +18,9 @@ pub fn call_threadsafe_function(callback: JsFunction) -> Result<()> {
 }
 
 #[napi]
-pub fn call_long_threadsafe_function(callback: JsFunction) -> Result<()> {
-  let tsfn: ThreadsafeFunction<u32, ErrorStrategy::CalleeHandled> =
-    callback.create_threadsafe_function(0, |ctx| Ok(vec![ctx.value + 1]))?;
+pub fn call_long_threadsafe_function(
+  tsfn: ThreadsafeFunction<u32, UnknownReturnValue>,
+) -> Result<()> {
   thread::spawn(move || {
     for n in 0..10 {
       thread::sleep(Duration::from_millis(100));
@@ -33,11 +31,11 @@ pub fn call_long_threadsafe_function(callback: JsFunction) -> Result<()> {
 }
 
 #[napi]
-pub fn threadsafe_function_throw_error(cb: JsFunction) -> Result<()> {
-  let tsfn: ThreadsafeFunction<bool, ErrorStrategy::CalleeHandled> =
-    cb.create_threadsafe_function(0, |ctx| ctx.env.get_boolean(ctx.value).map(|v| vec![v]))?;
+pub fn threadsafe_function_throw_error(
+  cb: ThreadsafeFunction<bool, UnknownReturnValue>,
+) -> Result<()> {
   thread::spawn(move || {
-    tsfn.call(
+    cb.call(
       Err(Error::new(
         Status::GenericFailure,
         "ThrowFromNative".to_owned(),
@@ -49,26 +47,23 @@ pub fn threadsafe_function_throw_error(cb: JsFunction) -> Result<()> {
 }
 
 #[napi]
-pub fn threadsafe_function_fatal_mode(cb: JsFunction) -> Result<()> {
-  let tsfn: ThreadsafeFunction<bool, ErrorStrategy::Fatal> =
-    cb.create_threadsafe_function(0, |ctx| ctx.env.get_boolean(ctx.value).map(|v| vec![v]))?;
+pub fn threadsafe_function_fatal_mode(
+  cb: ThreadsafeFunction<bool, UnknownReturnValue, false>,
+) -> Result<()> {
   thread::spawn(move || {
-    tsfn.call(true, ThreadsafeFunctionCallMode::Blocking);
+    cb.call(true, ThreadsafeFunctionCallMode::Blocking);
   });
   Ok(())
 }
 
 #[napi]
-pub fn threadsafe_function_fatal_mode_error(cb: JsFunction) -> Result<()> {
-  let tsfn: ThreadsafeFunction<bool, ErrorStrategy::Fatal> =
-    cb.create_threadsafe_function(0, |_ctx| {
-      Err::<Vec<JsBoolean>, Error>(Error::new(
-        Status::GenericFailure,
-        "Generic tsfn error".to_owned(),
-      ))
-    })?;
+pub fn threadsafe_function_fatal_mode_error(
+  cb: ThreadsafeFunction<bool, String, false>,
+) -> Result<()> {
   thread::spawn(move || {
-    tsfn.call(true, ThreadsafeFunctionCallMode::Blocking);
+    cb.call_with_return_value(true, ThreadsafeFunctionCallMode::Blocking, |ret, _| {
+      ret.map(|_| ())
+    });
   });
   Ok(())
 }
@@ -77,8 +72,8 @@ pub fn threadsafe_function_fatal_mode_error(cb: JsFunction) -> Result<()> {
 fn threadsafe_function_closure_capture(func: JsFunction) -> napi::Result<()> {
   let str = "test";
   let tsfn: ThreadsafeFunction<()> = func
-    .create_threadsafe_function(0, move |_| {
-      println!("{}", str); // str is NULL at this point
+    .create_threadsafe_function(move |_| {
+      println!("Captured in ThreadsafeFunction {}", str); // str is NULL at this point
       Ok(Vec::<JsString>::new())
     })
     .unwrap();
@@ -89,13 +84,12 @@ fn threadsafe_function_closure_capture(func: JsFunction) -> napi::Result<()> {
 }
 
 #[napi]
-pub fn tsfn_call_with_callback(func: JsFunction) -> napi::Result<()> {
-  let tsfn: ThreadsafeFunction<()> =
-    func.create_threadsafe_function(0, move |_| Ok(Vec::<JsString>::new()))?;
+pub fn tsfn_call_with_callback(tsfn: ThreadsafeFunction<(), String>) -> napi::Result<()> {
   tsfn.call_with_return_value(
     Ok(()),
     ThreadsafeFunctionCallMode::NonBlocking,
-    |value: String| {
+    |value: Result<String>, _| {
+      let value = value.expect("Failed to retrieve value from JS");
       println!("{}", value);
       assert_eq!(value, "ReturnFromJavaScriptRawCallback".to_owned());
       Ok(())
@@ -105,12 +99,11 @@ pub fn tsfn_call_with_callback(func: JsFunction) -> napi::Result<()> {
 }
 
 #[napi(ts_return_type = "Promise<void>")]
-pub fn tsfn_async_call(env: Env, func: JsFunction) -> napi::Result<Object> {
-  let tsfn: ThreadsafeFunction<()> =
-    func.create_threadsafe_function(0, move |_| Ok(vec![0u32, 1u32, 2u32]))?;
+pub fn tsfn_async_call(env: Env, func: Function<(u32, u32, u32), String>) -> napi::Result<Object> {
+  let tsfn = func.build_threadsafe_function().build()?;
 
   env.spawn_future(async move {
-    let msg: String = tsfn.call_async(Ok(())).await?;
+    let msg = tsfn.call_async((0, 1, 2)).await?;
     assert_eq!(msg, "ReturnFromJavaScriptRawCallback".to_owned());
     Ok(())
   })
@@ -124,7 +117,7 @@ pub fn accept_threadsafe_function(func: ThreadsafeFunction<u32>) {
 }
 
 #[napi]
-pub fn accept_threadsafe_function_fatal(func: ThreadsafeFunction<u32, ErrorStrategy::Fatal>) {
+pub fn accept_threadsafe_function_fatal(func: ThreadsafeFunction<u32, (), false>) {
   thread::spawn(move || {
     func.call(1, ThreadsafeFunctionCallMode::NonBlocking);
   });
@@ -141,15 +134,17 @@ pub fn accept_threadsafe_function_tuple_args(func: ThreadsafeFunction<(u32, bool
 }
 
 #[napi]
-pub async fn tsfn_return_promise(func: ThreadsafeFunction<u32>) -> Result<u32> {
-  let val = func.call_async::<Promise<u32>>(Ok(1)).await?.await?;
+pub async fn tsfn_return_promise(func: ThreadsafeFunction<u32, Promise<u32>>) -> Result<u32> {
+  let val = func.call_async(Ok(1)).await?.await?;
   Ok(val + 2)
 }
 
 #[napi]
-pub async fn tsfn_return_promise_timeout(func: ThreadsafeFunction<u32>) -> Result<u32> {
+pub async fn tsfn_return_promise_timeout(
+  func: ThreadsafeFunction<u32, Promise<u32>>,
+) -> Result<u32> {
   use tokio::time::{self, Duration};
-  let promise = func.call_async::<Promise<u32>>(Ok(1)).await?;
+  let promise = func.call_async(Ok(1)).await?;
   let sleep = time::sleep(Duration::from_nanos(1));
   tokio::select! {
     _ = sleep => {
@@ -162,6 +157,6 @@ pub async fn tsfn_return_promise_timeout(func: ThreadsafeFunction<u32>) -> Resul
 }
 
 #[napi]
-pub async fn tsfn_throw_from_js(tsfn: ThreadsafeFunction<u32>) -> napi::Result<u32> {
-  tsfn.call_async::<Promise<u32>>(Ok(42)).await?.await
+pub async fn tsfn_throw_from_js(tsfn: ThreadsafeFunction<u32, Promise<u32>>) -> napi::Result<u32> {
+  tsfn.call_async(Ok(42)).await?.await
 }
diff --git a/memory-testing/src/lib.rs b/memory-testing/src/lib.rs
index ce61119a..a6f2c9e3 100644
--- a/memory-testing/src/lib.rs
+++ b/memory-testing/src/lib.rs
@@ -2,7 +2,7 @@ use std::thread::spawn;
 
 use napi::{
   bindgen_prelude::*,
-  threadsafe_function::{ThreadSafeCallContext, ThreadsafeFunction, ThreadsafeFunctionCallMode},
+  threadsafe_function::{ThreadsafeCallContext, ThreadsafeFunction, ThreadsafeFunctionCallMode},
 };
 
 #[macro_use]
@@ -126,7 +126,7 @@ impl ChildReference {
 #[napi]
 pub fn leaking_func(env: Env, func: JsFunction) -> napi::Result<()> {
   let mut tsfn: ThreadsafeFunction<String> =
-    func.create_threadsafe_function(0, |mut ctx: ThreadSafeCallContext<String>| {
+    func.create_threadsafe_function(|mut ctx: ThreadsafeCallContext<String>| {
       ctx.env.adjust_external_memory(ctx.value.len() as i64)?;
       ctx
         .env
diff --git a/yarn.lock b/yarn.lock
index f802d97f..150f596a 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -533,6 +533,7 @@ __metadata:
     cross-env: "npm:7.0.3"
     electron: "npm:^29.0.1"
     lodash: "npm:^4.17.21"
+    rxjs: "npm:^7.8.1"
     sinon: "npm:^17.0.1"
     vite: "npm:^5.0.12"
     vite-plugin-node-polyfills: "npm:^0.19.0"