AsyncFunction() constructor
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2017.
Warning: The arguments passed to this constructor are dynamically parsed and executed as JavaScript. APIs like this are known as injection sinks, and are potentially a vector for cross-site-scripting (XSS) attacks.
You can mitigate this risk by always passing TrustedScript objects instead of strings and enforcing trusted types.
See Security considerations in the Function() constructor reference for more information.
The AsyncFunction() constructor creates AsyncFunction objects.
Note that AsyncFunction is not a global object. It can be obtained with the following code:
const AsyncFunction = async function () {}.constructor;
The AsyncFunction() constructor is not intended to be used directly, and all caveats mentioned in the Function() description apply to AsyncFunction().
Syntax
new AsyncFunction(functionBody)
new AsyncFunction(arg1, functionBody)
new AsyncFunction(arg1, arg2, functionBody)
new AsyncFunction(arg1, arg2, /* …, */ argN, functionBody)
AsyncFunction(functionBody)
AsyncFunction(arg1, functionBody)
AsyncFunction(arg1, arg2, functionBody)
AsyncFunction(arg1, arg2, /* …, */ argN, functionBody)
Note:
AsyncFunction() can be called with or without new. Both create a new AsyncFunction instance.
Parameters
See Function().
Examples
Note that these examples omit the use of trusted types for brevity. For code showing the recommended approach, see Using TrustedScript in eval().
Creating an async function from an AsyncFunction() constructor
function resolveAfter2Seconds(x) {
return new Promise((resolve) => {
setTimeout(() => {
resolve(x);
}, 2000);
});
}
const AsyncFunction = async function () {}.constructor;
const fn = new AsyncFunction(
"a",
"b",
"return await resolveAfter2Seconds(a) + await resolveAfter2Seconds(b);",
);
fn(10, 20).then((v) => {
console.log(v); // prints 30 after 4 seconds
});
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-async-function-constructor |