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.
The AsyncFunction() constructor creates AsyncFunction objects.
Note that AsyncFunction is not a global object. It can be obtained with the following code:
js
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
js
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
Creating an async function from an AsyncFunction() constructor
js
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® 2025 Language Specification # sec-async-function-constructor |
Browser compatibility
| desktop | mobile | server | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
AsyncFunction() constructor | ||||||||||||||