已废弃
This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

代理方法`handler.enumerate()`决定了被代理对象在`for...in`中的行为。不过这个方法已经在ES2016标准中被移除了。

## 语法

    var p = new Proxy(target, {
      enumerate(target) {
      }
    });

### 参数

下列参数将会被用以调用 `enumerate` 方法。this将会指向处理器对象。

`target`
  被代理的目标对象。

### Return value

该方法应当返回一个迭代器对象。

## 描述

`handler.enumerate` 方法决定了被代理对象在`for...in`时的行为。

### 触发条件

这些操作可以触发这个方法。

- for...in: `for (var name in proxy) {...}`
- `Reflect.enumerate()`

### Invariants

If the following invariants are violated, the proxy will throw a `TypeError`:

- The `enumerate` method must return an object.

## Examples

The following code traps `for...in` statements.

    var p = new Proxy({}, {
      enumerate(target) {
        console.log('called');
        return ['a', 'b', 'c'][Symbol.iterator]();
      }
    });

    for (var x in p) { // "called"
      console.log(x);  // "a"
    }                  // "b"
                       // "c"

The following code violates the invariant.

    var p = new Proxy({}, {
      enumerate(target) {
        return 1;
      }
    });

    for (var x in p) {} // TypeError is thrown

Note: Both examples make use of the shorthand syntax for method definitions.

## Specifications

Specification | Status | Comment
--- | --- | ---
ECMAScript 2015 (6th Edition, ECMA-262) [[Enumerate]] | Standard | Initial definition. Removed in ECMAScript 2016.

## Browser compatibility

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

| Desktop | Mobile | Server
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | Android webview | Chrome for Android | Edge Mobile | Firefox for Android | Opera for Android | Safari on iOS | Samsung Internet | Node.js
`enumerate` Deprecated Non-standard | Chrome No support No | Edge No support No | Firefox No support 37 — 47 | IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Edge Mobile No support No | Firefox Android No support 37 — 47 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No

### Legend

No support
  No support
Non-standard. Expect poor cross-browser support.
  Non-standard. Expect poor cross-browser support.
Deprecated. Not for use in new websites.
  Deprecated. Not for use in new websites.

## See also

- `Proxy`
- `handler`
- `for...in` statements
- `Reflect.enumerate()`