diff --git a/crates/backend/src/codegen/enum.rs b/crates/backend/src/codegen/enum.rs
index a8857afe..b016b577 100644
--- a/crates/backend/src/codegen/enum.rs
+++ b/crates/backend/src/codegen/enum.rs
@@ -38,6 +38,10 @@ impl NapiEnum {
         fn type_name() -> &'static str {
           #name_str
         }
+
+        fn value_type() -> napi::ValueType {
+          napi::ValueType::Object
+        }
       }
 
       impl ValidateNapiValue for #name {
diff --git a/crates/backend/src/codegen/struct.rs b/crates/backend/src/codegen/struct.rs
index e29cd9ba..c85d9dc7 100644
--- a/crates/backend/src/codegen/struct.rs
+++ b/crates/backend/src/codegen/struct.rs
@@ -16,6 +16,10 @@ fn gen_napi_value_map_impl(name: &Ident, to_napi_val_impl: TokenStream) -> Token
       fn type_name() -> &'static str {
         #name_str
       }
+
+      fn value_type() -> napi::ValueType {
+        napi::ValueType::Function
+      }
     }
 
     #to_napi_val_impl
@@ -255,6 +259,10 @@ impl NapiStruct {
         fn type_name() -> &'static str {
           #name_str
         }
+
+        fn value_type() -> napi::ValueType {
+          napi::ValueType::Object
+        }
       }
 
       impl ToNapiValue for #name {
diff --git a/crates/backend/src/typegen.rs b/crates/backend/src/typegen.rs
index f2404e8f..7839c9f8 100644
--- a/crates/backend/src/typegen.rs
+++ b/crates/backend/src/typegen.rs
@@ -59,6 +59,10 @@ static KNOWN_TYPES: Lazy<HashMap<&'static str, &'static str>> = Lazy::new(|| {
     ("Vec", "Array<{}>"),
     ("Option", "{} | null"),
     ("Result", "Error | {}"),
+    ("Either", "{} | {}"),
+    ("Either3", "{} | {} | {}"),
+    ("Either4", "{} | {} | {} | {}"),
+    ("Either5", "{} | {} | {} | {} | {}"),
   ]);
 
   map
diff --git a/crates/napi/src/bindgen_runtime/js_values.rs b/crates/napi/src/bindgen_runtime/js_values.rs
index 5e296f7c..7f35f72c 100644
--- a/crates/napi/src/bindgen_runtime/js_values.rs
+++ b/crates/napi/src/bindgen_runtime/js_values.rs
@@ -4,6 +4,7 @@ use std::ptr;
 mod array;
 mod boolean;
 mod buffer;
+mod either;
 mod map;
 mod nil;
 mod number;
@@ -14,6 +15,7 @@ mod string;
 
 pub use array::*;
 pub use buffer::*;
+pub use either::*;
 pub use nil::*;
 pub use object::*;
 pub use string::*;
@@ -23,6 +25,8 @@ pub use string::latin1_string::*;
 
 pub trait TypeName {
   fn type_name() -> &'static str;
+
+  fn value_type() -> ValueType;
 }
 
 pub trait ToNapiValue {
@@ -114,10 +118,14 @@ pub trait ValidateNapiValue: FromNapiValue + TypeName {
   }
 }
 
-impl<T> TypeName for Option<T> {
+impl<T: TypeName> TypeName for Option<T> {
   fn type_name() -> &'static str {
     "Option"
   }
+
+  fn value_type() -> ValueType {
+    T::value_type()
+  }
 }
 
 impl<T> FromNapiValue for Option<T>
diff --git a/crates/napi/src/bindgen_runtime/js_values/array.rs b/crates/napi/src/bindgen_runtime/js_values/array.rs
index c2500df5..3d9587f4 100644
--- a/crates/napi/src/bindgen_runtime/js_values/array.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/array.rs
@@ -74,6 +74,10 @@ impl TypeName for Array {
   fn type_name() -> &'static str {
     "Array"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::Object
+  }
 }
 
 impl ToNapiValue for Array {
@@ -122,6 +126,10 @@ impl<T> TypeName for Vec<T> {
   fn type_name() -> &'static str {
     "Array<T>"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::Object
+  }
 }
 
 impl<T> ToNapiValue for Vec<T>
diff --git a/crates/napi/src/bindgen_runtime/js_values/boolean.rs b/crates/napi/src/bindgen_runtime/js_values/boolean.rs
index ad061eca..b7398c8b 100644
--- a/crates/napi/src/bindgen_runtime/js_values/boolean.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/boolean.rs
@@ -4,6 +4,10 @@ impl TypeName for bool {
   fn type_name() -> &'static str {
     "bool"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::Boolean
+  }
 }
 
 impl ValidateNapiValue for bool {
diff --git a/crates/napi/src/bindgen_runtime/js_values/buffer.rs b/crates/napi/src/bindgen_runtime/js_values/buffer.rs
index 64024d8a..66fd324a 100644
--- a/crates/napi/src/bindgen_runtime/js_values/buffer.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/buffer.rs
@@ -52,6 +52,10 @@ impl TypeName for Buffer {
   fn type_name() -> &'static str {
     "Vec<u8>"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::Object
+  }
 }
 
 impl FromNapiValue for Buffer {
diff --git a/crates/napi/src/bindgen_runtime/js_values/either.rs b/crates/napi/src/bindgen_runtime/js_values/either.rs
new file mode 100644
index 00000000..192aa142
--- /dev/null
+++ b/crates/napi/src/bindgen_runtime/js_values/either.rs
@@ -0,0 +1,359 @@
+use super::{FromNapiValue, ToNapiValue, TypeName};
+use crate::{type_of, Status, ValueType};
+
+const ERROR_MSG: &str = "The return value of typeof(T) should not be equal in Either";
+
+#[derive(Debug, Clone, Copy)]
+pub enum Either<
+  A: TypeName + FromNapiValue + ToNapiValue,
+  B: TypeName + FromNapiValue + ToNapiValue,
+> {
+  A(A),
+  B(B),
+}
+
+impl<A: TypeName + FromNapiValue + ToNapiValue, B: TypeName + FromNapiValue + ToNapiValue> TypeName
+  for Either<A, B>
+{
+  fn type_name() -> &'static str {
+    "Either"
+  }
+
+  fn value_type() -> ValueType {
+    ValueType::Unknown
+  }
+}
+
+impl<A: TypeName + FromNapiValue + ToNapiValue, B: TypeName + FromNapiValue + ToNapiValue>
+  FromNapiValue for Either<A, B>
+{
+  unsafe fn from_napi_value(
+    env: napi_sys::napi_env,
+    napi_val: napi_sys::napi_value,
+  ) -> crate::Result<Self> {
+    debug_assert!(A::value_type() != B::value_type(), "{}", ERROR_MSG);
+    let js_type = type_of!(env, napi_val)?;
+    if js_type == A::value_type() {
+      A::from_napi_value(env, napi_val).map(Self::A)
+    } else if js_type == B::value_type() {
+      B::from_napi_value(env, napi_val).map(Self::B)
+    } else {
+      Err(crate::Error::new(
+        Status::InvalidArg,
+        format!(
+          "Expect type {} or {}, but got {}",
+          A::value_type(),
+          B::value_type(),
+          js_type
+        ),
+      ))
+    }
+  }
+}
+
+impl<A: TypeName + FromNapiValue + ToNapiValue, B: TypeName + FromNapiValue + ToNapiValue>
+  ToNapiValue for Either<A, B>
+{
+  unsafe fn to_napi_value(
+    env: napi_sys::napi_env,
+    value: Self,
+  ) -> crate::Result<crate::sys::napi_value> {
+    match value {
+      Self::A(a) => A::to_napi_value(env, a),
+      Self::B(b) => B::to_napi_value(env, b),
+    }
+  }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum Either3<
+  A: TypeName + FromNapiValue + ToNapiValue,
+  B: TypeName + FromNapiValue + ToNapiValue,
+  C: TypeName + FromNapiValue + ToNapiValue,
+> {
+  A(A),
+  B(B),
+  C(C),
+}
+
+impl<
+    A: TypeName + FromNapiValue + ToNapiValue,
+    B: TypeName + FromNapiValue + ToNapiValue,
+    C: TypeName + FromNapiValue + ToNapiValue,
+  > TypeName for Either3<A, B, C>
+{
+  fn type_name() -> &'static str {
+    "Either3"
+  }
+
+  fn value_type() -> ValueType {
+    ValueType::Unknown
+  }
+}
+
+impl<
+    A: TypeName + FromNapiValue + ToNapiValue,
+    B: TypeName + FromNapiValue + ToNapiValue,
+    C: TypeName + FromNapiValue + ToNapiValue,
+  > FromNapiValue for Either3<A, B, C>
+{
+  unsafe fn from_napi_value(
+    env: napi_sys::napi_env,
+    napi_val: napi_sys::napi_value,
+  ) -> crate::Result<Self> {
+    debug_assert!(
+      {
+        let mut types = vec![A::value_type(), B::value_type(), C::value_type()];
+        types.dedup();
+        types.len() == 3
+      },
+      "{}",
+      ERROR_MSG
+    );
+    let js_type = type_of!(env, napi_val)?;
+    if js_type == A::value_type() {
+      A::from_napi_value(env, napi_val).map(Self::A)
+    } else if js_type == B::value_type() {
+      B::from_napi_value(env, napi_val).map(Self::B)
+    } else if js_type == C::value_type() {
+      C::from_napi_value(env, napi_val).map(Self::C)
+    } else {
+      Err(crate::Error::new(
+        Status::InvalidArg,
+        format!(
+          "Expect type {} or {} or {}, but got {}",
+          A::value_type(),
+          B::value_type(),
+          C::value_type(),
+          js_type
+        ),
+      ))
+    }
+  }
+}
+
+impl<
+    A: TypeName + FromNapiValue + ToNapiValue,
+    B: TypeName + FromNapiValue + ToNapiValue,
+    C: TypeName + FromNapiValue + ToNapiValue,
+  > ToNapiValue for Either3<A, B, C>
+{
+  unsafe fn to_napi_value(
+    env: napi_sys::napi_env,
+    value: Self,
+  ) -> crate::Result<crate::sys::napi_value> {
+    match value {
+      Self::A(a) => A::to_napi_value(env, a),
+      Self::B(b) => B::to_napi_value(env, b),
+      Self::C(c) => C::to_napi_value(env, c),
+    }
+  }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum Either4<
+  A: TypeName + FromNapiValue + ToNapiValue,
+  B: TypeName + FromNapiValue + ToNapiValue,
+  C: TypeName + FromNapiValue + ToNapiValue,
+  D: TypeName + FromNapiValue + ToNapiValue,
+> {
+  A(A),
+  B(B),
+  C(C),
+  D(D),
+}
+
+impl<
+    A: TypeName + FromNapiValue + ToNapiValue,
+    B: TypeName + FromNapiValue + ToNapiValue,
+    C: TypeName + FromNapiValue + ToNapiValue,
+    D: TypeName + FromNapiValue + ToNapiValue,
+  > TypeName for Either4<A, B, C, D>
+{
+  fn type_name() -> &'static str {
+    "Either4"
+  }
+
+  fn value_type() -> ValueType {
+    ValueType::Unknown
+  }
+}
+
+impl<
+    A: TypeName + FromNapiValue + ToNapiValue,
+    B: TypeName + FromNapiValue + ToNapiValue,
+    C: TypeName + FromNapiValue + ToNapiValue,
+    D: TypeName + FromNapiValue + ToNapiValue,
+  > FromNapiValue for Either4<A, B, C, D>
+{
+  unsafe fn from_napi_value(
+    env: napi_sys::napi_env,
+    napi_val: napi_sys::napi_value,
+  ) -> crate::Result<Self> {
+    debug_assert!(
+      {
+        let mut types = vec![
+          A::value_type(),
+          B::value_type(),
+          C::value_type(),
+          D::value_type(),
+        ];
+        types.dedup();
+        types.len() == 4
+      },
+      "{}",
+      ERROR_MSG
+    );
+    let js_type = type_of!(env, napi_val)?;
+    if js_type == A::value_type() {
+      A::from_napi_value(env, napi_val).map(Self::A)
+    } else if js_type == B::value_type() {
+      B::from_napi_value(env, napi_val).map(Self::B)
+    } else if js_type == C::value_type() {
+      C::from_napi_value(env, napi_val).map(Self::C)
+    } else if js_type == D::value_type() {
+      D::from_napi_value(env, napi_val).map(Self::D)
+    } else {
+      Err(crate::Error::new(
+        Status::InvalidArg,
+        format!(
+          "Expect type {} or {} or {} or {}, but got {}",
+          A::value_type(),
+          B::value_type(),
+          C::value_type(),
+          D::value_type(),
+          js_type
+        ),
+      ))
+    }
+  }
+}
+
+impl<
+    A: TypeName + FromNapiValue + ToNapiValue,
+    B: TypeName + FromNapiValue + ToNapiValue,
+    C: TypeName + FromNapiValue + ToNapiValue,
+    D: TypeName + FromNapiValue + ToNapiValue,
+  > ToNapiValue for Either4<A, B, C, D>
+{
+  unsafe fn to_napi_value(
+    env: napi_sys::napi_env,
+    value: Self,
+  ) -> crate::Result<crate::sys::napi_value> {
+    match value {
+      Self::A(a) => A::to_napi_value(env, a),
+      Self::B(b) => B::to_napi_value(env, b),
+      Self::C(c) => C::to_napi_value(env, c),
+      Self::D(d) => D::to_napi_value(env, d),
+    }
+  }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum Either5<
+  A: TypeName + FromNapiValue + ToNapiValue,
+  B: TypeName + FromNapiValue + ToNapiValue,
+  C: TypeName + FromNapiValue + ToNapiValue,
+  D: TypeName + FromNapiValue + ToNapiValue,
+  E: TypeName + FromNapiValue + ToNapiValue,
+> {
+  A(A),
+  B(B),
+  C(C),
+  D(D),
+  E(E),
+}
+
+impl<
+    A: TypeName + FromNapiValue + ToNapiValue,
+    B: TypeName + FromNapiValue + ToNapiValue,
+    C: TypeName + FromNapiValue + ToNapiValue,
+    D: TypeName + FromNapiValue + ToNapiValue,
+    E: TypeName + FromNapiValue + ToNapiValue,
+  > TypeName for Either5<A, B, C, D, E>
+{
+  fn type_name() -> &'static str {
+    "Either5"
+  }
+
+  fn value_type() -> ValueType {
+    ValueType::Unknown
+  }
+}
+
+impl<
+    A: TypeName + FromNapiValue + ToNapiValue,
+    B: TypeName + FromNapiValue + ToNapiValue,
+    C: TypeName + FromNapiValue + ToNapiValue,
+    D: TypeName + FromNapiValue + ToNapiValue,
+    E: TypeName + FromNapiValue + ToNapiValue,
+  > FromNapiValue for Either5<A, B, C, D, E>
+{
+  unsafe fn from_napi_value(
+    env: napi_sys::napi_env,
+    napi_val: napi_sys::napi_value,
+  ) -> crate::Result<Self> {
+    debug_assert!(
+      {
+        let mut types = vec![
+          A::value_type(),
+          B::value_type(),
+          C::value_type(),
+          D::value_type(),
+          E::value_type(),
+        ];
+        types.dedup();
+        types.len() == 5
+      },
+      "{}",
+      ERROR_MSG
+    );
+    let js_type = type_of!(env, napi_val)?;
+    if js_type == A::value_type() {
+      A::from_napi_value(env, napi_val).map(Self::A)
+    } else if js_type == B::value_type() {
+      B::from_napi_value(env, napi_val).map(Self::B)
+    } else if js_type == C::value_type() {
+      C::from_napi_value(env, napi_val).map(Self::C)
+    } else if js_type == D::value_type() {
+      D::from_napi_value(env, napi_val).map(Self::D)
+    } else if js_type == E::value_type() {
+      E::from_napi_value(env, napi_val).map(Self::E)
+    } else {
+      Err(crate::Error::new(
+        Status::InvalidArg,
+        format!(
+          "Expect type {} or {} or {} or {} or {}, but got {}",
+          A::value_type(),
+          B::value_type(),
+          C::value_type(),
+          D::value_type(),
+          E::value_type(),
+          js_type
+        ),
+      ))
+    }
+  }
+}
+
+impl<
+    A: TypeName + FromNapiValue + ToNapiValue,
+    B: TypeName + FromNapiValue + ToNapiValue,
+    C: TypeName + FromNapiValue + ToNapiValue,
+    D: TypeName + FromNapiValue + ToNapiValue,
+    E: TypeName + FromNapiValue + ToNapiValue,
+  > ToNapiValue for Either5<A, B, C, D, E>
+{
+  unsafe fn to_napi_value(
+    env: napi_sys::napi_env,
+    value: Self,
+  ) -> crate::Result<crate::sys::napi_value> {
+    match value {
+      Self::A(a) => A::to_napi_value(env, a),
+      Self::B(b) => B::to_napi_value(env, b),
+      Self::C(c) => C::to_napi_value(env, c),
+      Self::D(d) => D::to_napi_value(env, d),
+      Self::E(e) => E::to_napi_value(env, e),
+    }
+  }
+}
diff --git a/crates/napi/src/bindgen_runtime/js_values/map.rs b/crates/napi/src/bindgen_runtime/js_values/map.rs
index ddbd33e0..f91e7c51 100644
--- a/crates/napi/src/bindgen_runtime/js_values/map.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/map.rs
@@ -7,6 +7,10 @@ impl<K, V> TypeName for HashMap<K, V> {
   fn type_name() -> &'static str {
     "HashMap"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::Object
+  }
 }
 
 impl<K, V> ToNapiValue for HashMap<K, V>
diff --git a/crates/napi/src/bindgen_runtime/js_values/nil.rs b/crates/napi/src/bindgen_runtime/js_values/nil.rs
index 50177192..11971b93 100644
--- a/crates/napi/src/bindgen_runtime/js_values/nil.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/nil.rs
@@ -9,6 +9,10 @@ impl TypeName for Null {
   fn type_name() -> &'static str {
     "null"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::Null
+  }
 }
 
 impl ValidateNapiValue for Null {
@@ -46,6 +50,10 @@ impl TypeName for Undefined {
   fn type_name() -> &'static str {
     "undefined"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::Undefined
+  }
 }
 
 impl ValidateNapiValue for Undefined {
diff --git a/crates/napi/src/bindgen_runtime/js_values/number.rs b/crates/napi/src/bindgen_runtime/js_values/number.rs
index 1c49a938..457b0ad4 100644
--- a/crates/napi/src/bindgen_runtime/js_values/number.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/number.rs
@@ -8,6 +8,10 @@ macro_rules! impl_number_conversions {
         fn type_name() -> &'static str {
           $name
         }
+
+        fn value_type() -> crate::ValueType {
+          crate::ValueType::Number
+        }
       }
 
       impl $crate::bindgen_prelude::ValidateNapiValue for $t {
diff --git a/crates/napi/src/bindgen_runtime/js_values/object.rs b/crates/napi/src/bindgen_runtime/js_values/object.rs
index 2d08c3af..4729b274 100644
--- a/crates/napi/src/bindgen_runtime/js_values/object.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/object.rs
@@ -81,6 +81,10 @@ impl TypeName for Object {
   fn type_name() -> &'static str {
     "Object"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::Object
+  }
 }
 
 impl ToNapiValue for Object {
diff --git a/crates/napi/src/bindgen_runtime/js_values/string.rs b/crates/napi/src/bindgen_runtime/js_values/string.rs
index bad667bd..cc07a9db 100644
--- a/crates/napi/src/bindgen_runtime/js_values/string.rs
+++ b/crates/napi/src/bindgen_runtime/js_values/string.rs
@@ -11,6 +11,10 @@ impl TypeName for String {
   fn type_name() -> &'static str {
     "String"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::String
+  }
 }
 
 impl ToNapiValue for String {
@@ -61,6 +65,10 @@ impl TypeName for &str {
   fn type_name() -> &'static str {
     "String"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::String
+  }
 }
 
 impl ToNapiValue for &str {
@@ -96,6 +104,10 @@ impl TypeName for Utf16String {
   fn type_name() -> &'static str {
     "String(utf16)"
   }
+
+  fn value_type() -> ValueType {
+    ValueType::String
+  }
 }
 
 impl FromNapiValue for Utf16String {
@@ -181,6 +193,10 @@ pub mod latin1_string {
     fn type_name() -> &'static str {
       "String(latin1)"
     }
+
+    fn value_type() -> ValueType {
+      ValueType::String
+    }
   }
 
   #[cfg(feature = "latin1")]
diff --git a/examples/napi/__test__/typegen.spec.ts.md b/examples/napi/__test__/typegen.spec.ts.md
index 4f4a206f..75aac183 100644
--- a/examples/napi/__test__/typegen.spec.ts.md
+++ b/examples/napi/__test__/typegen.spec.ts.md
@@ -14,6 +14,13 @@ Generated by [AVA](https://avajs.dev).
     export function readFileAsync(path: string): Promise<Buffer>␊
     export function getCwd(callback: (arg0: string) => void): void␊
     export function readFile(callback: (arg0: Error | undefined, arg1: string | null) => void): void␊
+    export function eitherStringOrNumber(input: string | number): number␊
+    export function returnEither(input: number): string | number␊
+    export function either3(input: string | number | boolean): number␊
+    interface Obj {␊
+      v: string | number␊
+    }␊
+    export function either4(input: string | number | boolean | Obj): number␊
     export enum Kind { Dog = 0, Cat = 1, Duck = 2 }␊
     export enum CustomNumEnum { One = 1, Two = 2, Three = 3, Four = 4, Six = 6, Eight = 8, Nine = 9, Ten = 10 }␊
     export function enumToI32(e: CustomNumEnum): number␊
diff --git a/examples/napi/__test__/typegen.spec.ts.snap b/examples/napi/__test__/typegen.spec.ts.snap
index d423c065..bf6d133e 100644
Binary files a/examples/napi/__test__/typegen.spec.ts.snap and b/examples/napi/__test__/typegen.spec.ts.snap differ
diff --git a/examples/napi/__test__/values.spec.ts b/examples/napi/__test__/values.spec.ts
index fca2a6a8..c9c01474 100644
--- a/examples/napi/__test__/values.spec.ts
+++ b/examples/napi/__test__/values.spec.ts
@@ -26,6 +26,10 @@ import {
   getPackageJsonName,
   getBuffer,
   readFileAsync,
+  eitherStringOrNumber,
+  returnEither,
+  either3,
+  either4,
 } from '../'
 
 test('number', (t) => {
@@ -130,3 +134,29 @@ test('async', async (t) => {
 
   await t.throwsAsync(() => readFileAsync('some_nonexist_path.file'))
 })
+
+test('either', (t) => {
+  t.is(eitherStringOrNumber(2), 2)
+  t.is(eitherStringOrNumber('hello'), 'hello'.length)
+})
+
+test('return either', (t) => {
+  t.is(returnEither(2), 2)
+  t.is(returnEither(42), '42')
+})
+
+test('either3', (t) => {
+  t.is(either3(2), 2)
+  t.is(either3('hello'), 'hello'.length)
+  t.is(either3(true), 1)
+  t.is(either3(false), 0)
+})
+
+test('either4', (t) => {
+  t.is(either4(2), 2)
+  t.is(either4('hello'), 'hello'.length)
+  t.is(either4(true), 1)
+  t.is(either4(false), 0)
+  t.is(either4({ v: 1 }), 1)
+  t.is(either4({ v: 'world' }), 'world'.length)
+})
diff --git a/examples/napi/index.d.ts b/examples/napi/index.d.ts
index d251a91d..54b6e118 100644
--- a/examples/napi/index.d.ts
+++ b/examples/napi/index.d.ts
@@ -4,6 +4,13 @@ export function sumNums(nums: Array<number>): number
 export function readFileAsync(path: string): Promise<Buffer>
 export function getCwd(callback: (arg0: string) => void): void
 export function readFile(callback: (arg0: Error | undefined, arg1: string | null) => void): void
+export function eitherStringOrNumber(input: string | number): number
+export function returnEither(input: number): string | number
+export function either3(input: string | number | boolean): number
+interface Obj {
+  v: string | number
+}
+export function either4(input: string | number | boolean | Obj): number
 export enum Kind { Dog = 0, Cat = 1, Duck = 2 }
 export enum CustomNumEnum { One = 1, Two = 2, Three = 3, Four = 4, Six = 6, Eight = 8, Nine = 9, Ten = 10 }
 export function enumToI32(e: CustomNumEnum): number
diff --git a/examples/napi/src/either.rs b/examples/napi/src/either.rs
new file mode 100644
index 00000000..12ddccdc
--- /dev/null
+++ b/examples/napi/src/either.rs
@@ -0,0 +1,57 @@
+use napi::bindgen_prelude::*;
+
+#[napi]
+fn either_string_or_number(input: Either<String, u32>) -> u32 {
+  match input {
+    Either::A(s) => s.len() as u32,
+    Either::B(n) => n,
+  }
+}
+
+#[napi]
+fn return_either(input: u32) -> Either<String, u32> {
+  if input > 10 {
+    Either::A(format!("{}", input))
+  } else {
+    Either::B(input)
+  }
+}
+
+#[napi]
+fn either3(input: Either3<String, u32, bool>) -> u32 {
+  match input {
+    Either3::A(s) => s.len() as u32,
+    Either3::B(n) => n,
+    Either3::C(b) => {
+      if b {
+        1
+      } else {
+        0
+      }
+    }
+  }
+}
+
+#[napi(object)]
+struct Obj {
+  pub v: Either<String, u32>,
+}
+
+#[napi]
+fn either4(input: Either4<String, u32, bool, Obj>) -> u32 {
+  match input {
+    Either4::A(s) => s.len() as u32,
+    Either4::B(n) => n,
+    Either4::C(b) => {
+      if b {
+        1
+      } else {
+        0
+      }
+    }
+    Either4::D(f) => match f.v {
+      Either::A(s) => s.len() as u32,
+      Either::B(n) => n,
+    },
+  }
+}
diff --git a/examples/napi/src/lib.rs b/examples/napi/src/lib.rs
index 057d6756..b739a35f 100644
--- a/examples/napi/src/lib.rs
+++ b/examples/napi/src/lib.rs
@@ -7,6 +7,7 @@ mod array;
 mod r#async;
 mod callback;
 mod class;
+mod either;
 mod r#enum;
 mod error;
 mod nullable;