Generator

Obiekt Generator jest zwracany przez generator function i odpowiada obu: iterable protocol i iterator protocol.

function* gen() {
  yield 1;
  yield 2;
  yield 3;
}

var g = gen(); // "Generator { }"

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.

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
// ...

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).

Generator.prototype.next()

Returns a value yielded by the yield expression. This corresponds to next() in the ES2015 generator object.

Generator.prototype.close()

Closes the generator, so that when calling next() an StopIteration error will be thrown. This corresponds to the return() 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 next yield expression. send(x) corresponds to next(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.

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)

• The legacy generator function
• The legacy generator function expression
• StopIteration
• The legacy Iterator protocol

• Functions
• function
• function expression
• Function
• function*
• function* expression
• GeneratorFunction
• The Iterator protocol