## 概述

`multiline` 属性表明正则表达式是否使用了 "`m`" 标志。`multiline` 是正则表达式实例的一个只读属性。

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

## 描述

`multiline` 是一个布尔对象，如果使用了 "`m`" 标志，则返回 `true`；否则，返回 `false`。"`m`" 标志意味着一个多行输入字符串被看作多行。例如，使用 "`m`"，"`^`" 和 "`$`" 将会从只匹配正则字符串的开头或结尾，变为匹配字符串中任一行的开头或结尾。

你无法直接更改此属性。

## 示例

### 例子：使用 `multiline`

    var regex = new RegExp("foo", "m")

    console.log(regex.multiline) // true

## 规范

Specification | Status | Comment
--- | --- | ---
ECMAScript 3rd Edition. Implemented in JavaScript 1.2. | Standard | Initial definition. JavaScript 1.5: `multiline` is a property of a `RegExp` instance, not the `RegExp` object.
ECMAScript 5.1 (ECMA-262) RegExp.prototype.multiline | Standard |
ECMAScript 2015 (6th Edition, ECMA-262) RegExp.prototype.multiline | Standard | `multiline` is now a prototype accessor property rather than an instance's own data property.

## 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) | (Yes) | (Yes) | (Yes) | (Yes)

Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile
--- | --- | --- | --- | --- | --- | ---
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes)

## 相关链接

- `RegExp.prototype.global`
- `RegExp.prototype.lastIndex`
- `RegExp.prototype.ignoreCase`
- `RegExp.prototype.source`
- `RegExp.prototype.sticky`