function* expression
The function*
keyword can be used to define a generator function inside an expression.
You can also define generator functions using the function*
declaration.
{{EmbedInteractiveExample("pages/js/expressions-functionasteriskexpression.html", "taller")}}
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
}
[!NOTE] An expression statement cannot begin with the keyword
function
to avoid ambiguity with afunction*
declaration. Thefunction
keyword only begins an expression when it appears in a context that cannot accept statements.
Parameters
name
{{optional_inline}}- : The function name. Can be omitted, in which case the function is anonymous. The name is only local to the function body.
paramN
{{optional_inline}}- : The name of a formal parameter for the function. For the parameters' syntax, see the Functions reference.
statements
{{optional_inline}}- : The statements which comprise the body of the function.
Description
A function*
expression is very similar to, and has almost the same syntax as, a function*
declaration. The main difference between a function*
expression and a function*
declaration is the function name, which can be omitted in function*
expressions to create anonymous functions. A 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 iterable iterator object. See also the chapter about functions for more information.
Examples
Using function* expression
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;
};
Specifications
Browser compatibility
See also
- Functions guide
- Functions
- {{jsxref("Statements/function*", "function*")}}
- {{jsxref("GeneratorFunction")}}
- Iteration protocols
- {{jsxref("Operators/yield", "yield")}}
- {{jsxref("Operators/yield*", "yield*")}}