> For the complete documentation index, see [llms.txt](https://deemolover.gitbook.io/log-os/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://deemolover.gitbook.io/log-os/programming-languages/javascript/iterator-and-generator.md).

# Iterator & Generator

## Iterator

> an iterator is any object which implements the [Iterator protocol](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#the_iterator_protocol) by having a `next()` method that returns an object with two properties:
>
> `value`The next value in the iteration sequence.
>
> `done`This is `true` if the last value in the sequence has already been consumed. If `value` is present alongside `done`, it is the iterator's return value.

## Iterable

满足 Iterable Protocol 的对象可以被 for of 遍历。

> In order to be **iterable**, an object must implement the **`@@iterator`** method, meaning that the object (or one of the objects up its [prototype chain](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain)) must have a property with a `@@iterator` key which is available via constant [`Symbol.iterator`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/iterator) .

Iterable Protocol 要求通过取 \[Symbol.iterator] 属性应当可以获得一个函数（也就是说这是它的一个成员方法），这个函数返回一个 iterator。

## Generator

```javascript
// 生成器
function *createIterator() {
    yield 1;
    yield 2;
    yield 3;
}
// 生成器能像正规函数那样被调用，但会返回一个迭代器
let iterator = createIterator();
console.log(iterator.next().value); // 1
console.log(iterator.next().value); // 2
console.log(iterator.next().value); // 3
```

## Reference

\[1] <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Iterators_and_Generators>

\[2] <https://www.cnblogs.com/xiaohuochai/p/7253466.html>

\[3] <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols>