The async function* keywords can be used to define an async generator function inside an expression.
You can also define async generator functions using the async function* declaration.
The async function* keywords can be used to define an async generator function inside an expression.
You can also define async generator functions using the async function* declaration.
async function joinAll(generator) {
let str = "";
for await (const val of generator()) {
str += val;
}
return str;
}
joinAll(async function* () {
yield await Promise.resolve("a");
yield await Promise.resolve("b");
yield await Promise.resolve("c");
}).then((str) => console.log(str));
/ Expected output: "abc"
async function* (param0) {
statements
}
async function* (param0, param1) {
statements
}
async function* (param0, param1, /* …, */ paramN) {
statements
}
async function* name(param0) {
statements
}
async function* name(param0, param1) {
statements
}
async function* name(param0, param1, /* …, */ paramN) {
statements
}
Note:
An async function* declaration. The async function keywords only begin an expression when they appear in a context that cannot accept statements.
name OptionalThe function name. Can be omitted, in which case the function is anonymous. The name is only local to the function body.
paramN OptionalThe name of a formal parameter for the function. For the parameters' syntax, see the Functions reference.
statements OptionalThe statements which comprise the body of the function.
An async function* expression is very similar to, and has almost the same syntax as, an functions for more information.
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);
};
x(6)
.next()
.then((res) => console.log(res.value)); / 36
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-async-generator-function-definitions |