`flags`属性返回一个字符串，由当前正则表达式对象的标志组成。

`RegExp.prototype.flags` 属性的属性特性：
writable | false
enumerable | false
configurable | true

## 描述

`flags`属性中的标志以字典序排序（从左到右，即`"gimuy"`）。

## 示例

### 使用`flags`

    /foo/ig.flags;   // "gi"
    /bar/myu.flags;  // "muy"

## Polyfill

    if (RegExp.prototype.flags === undefined) {
      Object.defineProperty(RegExp.prototype, 'flags', {
        configurable: true,
        get: function() {
          return this.toString().match(/[gimuy]*$/)[0];
        }
      });
    }

## 规范

Specification | Status | Comment
--- | --- | ---
ECMAScript 2015 (6th Edition, ECMA-262) RegExp.prototype.flags | Standard | 初始定义。
ECMAScript Latest Draft (ECMA-262) RegExp.prototype.flags | Draft |

## 浏览器兼容性

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!

- Desktop
- Mobile

Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari
--- | --- | --- | --- | --- | ---
Basic support | (Yes) | 37 (37) | 未实现 | 未实现 | 未实现

Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile
--- | --- | --- | --- | --- | --- | ---
Basic support | 未实现 | 未实现 | 37.0 (37) | 未实现 | 未实现 | 未实现

## 另见

- `RegExp.prototype.source`