async function* expression

The async function* keywords can be used to define an asynchronous generator function inside an expression.

You can also define async generator functions using the async function* declaration.

Try it


async function* (param0) {
async function* (param0, param1) {
async function* (param0, param1, /* … ,*/ paramN) {

async function* name(param0) {
async function* name(param0, param1) {
async function* name(param0, param1, /* … ,*/ paramN) {

Note: An expression statement cannot begin with the keywords async function to avoid ambiguity with an async function* declaration. The async function keywords only begin an expression when they appear in a context that cannot accept statements.


name Optional

The function name. Can be omitted, in which case the function is anonymous. The name is only local to the function body.

paramN Optional

The name of an argument to be passed to the function.

statements Optional

The statements which comprise the body of the function.


An async function* expression is very similar to, and has almost the same syntax as, an async function* declaration. The main difference between an async function* expression and an async function* declaration is the function name, which can be omitted in async function* expressions to create anonymous functions. An async function* expression can be used as an IIFE (Immediately Invoked Function Expression) which runs as soon as it is defined, allowing you to create an ad-hoc async iterable object. See also the chapter about functions for more information.


Using async function*

The following example defines an unnamed asynchronous generator function and assigns it to x. The function yields the square of its argument:

const x = async function* (y) {
  yield Promise.resolve(y * y);
  .then((res) => console.log(res.value)); // 36


ECMAScript Language Specification
# sec-async-generator-function-definitions

Browser compatibility

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See also