The function* keyword can be used to define a generator function inside an expression.
You can also define generator functions using the function* declaration.
The function* keyword can be used to define a generator function inside an expression.
You can also define generator functions using the function* declaration.
const foo = function* () {
yield "a";
yield "b";
yield "c";
};
let str = "";
for (const val of foo()) {
str += val;
}
console.log(str);
/ Expected output: "abc"
function* (param0) {
statements
}
function* (param0, param1) {
statements
}
function* (param0, param1, /* …, */ paramN) {
statements
}
function* name(param0) {
statements
}
function* name(param0, param1) {
statements
}
function* name(param0, param1, /* …, */ paramN) {
statements
}
Note:
An function* declaration. The function keyword only begins an expression when it appears 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.
A function* expression is very similar to, and has almost the same syntax as, a functions for more information.
The following example defines an unnamed generator function and assigns it to x. The function yields the square of its argument:
const x = function* (y) {
yield y * y;
};
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-generator-function-definitions |