Thefunction* keyword can be used to define a generator function inside an expression.

You can also define generator functions using thefunction* declaration.

Try it

const foo = function* () {  yield "a";  yield "b";  yield "c";};let str = "";for (const val of foo()) {  str += val;}console.log(str);// Expected output: "abc"

Syntax

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}

Parameters

nameOptional

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

paramNOptional

The name of a formal parameter for the function. For the parameters' syntax, see theFunctions reference.

statementsOptional

The statements which comprise the body of the function.

Description

Afunction* expression is very similar to, and has almost the same syntax as, afunction* declaration. The main difference between afunction* expression and afunction* declaration is thefunction name, which can be omitted infunction* expressions to createanonymous functions. Afunction* expression can be used as anIIFE (Immediately Invoked Function Expression) which runs as soon as it is defined, allowing you to create an ad-hociterable iterator object. See also the chapter aboutfunctions for more information.

Examples

Using function* expression

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

const x = function* (y) {  yield y * y;};

Specifications

Browser compatibility

See also

• Functions guide
• Functions
• function*
• GeneratorFunction
• Iteration protocols
• yield
• yield*