diff --git a/src/syscall/js/promise.go b/src/syscall/js/promise.go
new file mode 100644
index 00000000000000..afa784574bc88a
--- /dev/null
+++ b/src/syscall/js/promise.go
@@ -0,0 +1,57 @@
+//go:build js && wasm
+
+package js
+
+import "errors"
+
+// Promisable function that satisfies MakePromise's requirements.
+type PromiseAbleFunc = func(Value, []Value) (interface{}, error)
+
+// MakePromise makes a promise of a function that takes an array of arguments.
+func PromiseOf(fn PromiseAbleFunc) Func {
+	return FuncOf(func(this Value, args []Value) interface{} {
+		// Handler for this Promise.
+		handler := FuncOf(func(promiseThis Value, promiseArgs []Value) interface{} {
+			resolve := promiseArgs[0]
+			reject := promiseArgs[1]
+
+			// Run this asynchronously.
+			go func() {
+				// Recover by rejecting.
+				defer func() {
+					if err := recover(); err != nil {
+						reject.Invoke(PromiseError(err))
+					}
+				}()			
+				
+				// Run the PromiseAble func with original this and args.
+				res, err := fn(this, args)
+				if err != nil {
+					reject.Invoke(PromiseError(err))
+					return
+				}
+				resolve.Invoke(res)
+			}()
+
+			// Handler doesn't return anything directly.
+			return nil
+		})
+
+		// Create the Promise and return.
+		promiseConstructor := Global().Get("Promise")
+		return promiseConstructor.New(handler)
+	})
+}
+
+// PromiseError makes sure to return some error that Invoke will understand.
+func PromiseError(e interface{}) (err error) {
+	switch x := e.(type) {
+	case string:
+		err = errors.New(x)
+	case error:
+		err = x
+	default:
+		err = errors.New("unknown panic")
+	}
+	return err
+}
</div><div class="naked_ctrl">
<form action="/index.cgi/contrast" method="get" name="gate">
<p><a href="http://altstyle.alfasado.net">AltStyle</a> によって変換されたページ <a href="https://patch-diff.githubusercontent.com/raw/golang/go/pull/52581.diff">(-&gt;オリジナル)</a>
/ <label>アドレス: <input type="text" name="naked_post_url" value="https://patch-diff.githubusercontent.com/raw/golang/go/pull/52581.diff" size="22" /></label> <label>モード: <select name="naked_post_mode">
<option value="default">デフォルト</option>
<option value="speech">音声ブラウザ</option>
<option value="ruby">ルビ付き</option>
<option value="contrast" selected="selected">配色反転</option>
<option value="larger-text">文字拡大</option>
<option value="mobile">モバイル</option>
</select>
<input type="submit" value="表示" />
</p>
</form>
</div>