Obiekt Generator
jest zwracany przez generator function i odpowiada obu: iterable protocol i iterator protocol.
Syntax
function* gen() { yield 1; yield 2; yield 3; } var g = gen(); // "Generator { }"
Methods
Generator.prototype.next()
- Returns a value yielded by the
yield
expression. Generator.prototype.return()
- Returns the given value and finishes the generator.
Generator.prototype.throw()
- Throws an error to a generator.
Example
An infinite iterator
function* idMaker() {
var index = 0;
while(true)
yield index++;
}
var gen = idMaker(); // "Generator { }"
console.log(gen.next().value); // 0
console.log(gen.next().value); // 1
console.log(gen.next().value); // 2
// ...
Legacy generator objects
Firefox (SpiderMonkey) also implements an earlier version of generators in JavaScript 1.7, where the star (*) in the function declaration was not necessary (you just use the yield
keyword in the function body). However, legacy generators are deprecated. Do not use them; they are going to be removed (błąd 1083482).
Legacy generator methods
Generator.prototype.next()
- Returns a value yielded by the
yield
expression. This corresponds tonext()
in the ES2015 generator object. Generator.prototype.close()
- Closes the generator, so that when calling
next()
anStopIteration
error will be thrown. This corresponds to thereturn()
method in the ES2015 generator object. Generator.prototype.send()
- Used to send a value to a generator. The value is returned from the
yield
expression, and returns a value yielded by the nextyield
expression.send(x)
corresponds tonext(x)
in the ES2015 generator object. Generator.
prototype.
throw()
- Throws an error to a generator. This corresponds to the
throw()
method in the ES2015 generator object.
Legacy generator example
function fibonacci() {
var a = yield 1;
yield a * 2;
}
var it = fibonacci();
console.log(it); // "Generator { }"
console.log(it.next()); // 1
console.log(it.send(10)); // 20
console.log(it.close()); // undefined
console.log(it.next()); // throws StopIteration (as the generator is now closed)
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Generator objects' in that specification. |
Standard | Initial definition. |
ECMAScript (ECMA-262) The definition of 'Generator objects' in that specification. |
Living Standard |
Browser compatibility
We're converting our compatibility data into a machine-readable JSON format.
This compatibility table still uses the old format,
because we haven't yet converted the data it contains.
Find out how you can help!
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 39.0 | (Yes) | No support | No support | No support |
Feature | Android | Android Webview | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|
Basic support | No support | 39.0 | (Yes) | No support | No support | No support | 39.0 |