Iterator : Object

An Iterator is an Object that returns a sequence of values.

You can use the **for(var value of iterator) {}** to easily loop

over the values in an iterator.

Calling an ECMAScript 2015 generator function (**function*() {}**) return

an Iterator.

You may create your own %%/Iterable|Iterable%% object by assigning the

%%/Symbol#iterator|**Symbol.iterator**%% property to an

object with a **next()** method.

Version:

ECMAScript 2015

Spec:

http://www.ecma-international.org/ecma-262/6.0/#sec-iterator-interface

----

instance.next([yieldValue : Object]) : { value : Object, done : Boolean }

Returns an object containing the next value in the iterator.

If all items have been returned, **done** will be **true**.

For generator functions, **yieldValue** is returned to the generator

from the **yield** statement.

<example>

// Generator functions create iterators when called

var generator = function*() {

yield 'foo';

var yieldValue = yield 'bar';

console.log('generator yieldValue = ' + yieldValue);

console.log();

};

// Usually you will iterate over it using for (... of ...)

// which will call next() for you automatically

for (var item of generator()) {

console.log(item);

}

// You can also get the iterator and manually call next()

var iterator = generator();

console.dir(iterator.next());

console.dir(iterator.next());

console.dir(iterator.next('passed to next'));

// You can create iterable objects manually

var myIterable = { };

myIterable[Symbol.iterator] = function() {

var count = 0;

return {

next: function() {

if (count >= 2) return { value: undefined, done: true };

count++;

return { value: 'my item' + count, done: false };

}

}

};

// Using for (... of ...) calls the next() defined above

for (var item of myIterable) {

console.log(item);

}

// You can also call it manually

iterator = myIterable[Symbol.iterator]();

console.dir(iterator.next());

console.dir(iterator.next());

console.dir(iterator.next());

</example>