全局属性 `Infinity` 是一个数值，表示无穷大。

`Infinity` 属性的属性特性：
writable | false
enumerable | false
configurable | false

## 语法

    Infinity

## 描述

`Infinity` 是全局对象（global object）的一个属性，即它是一个全局变量。

`Infinity` 的初始值是 `Number.POSITIVE_INFINITY`。`Infinity`（正无穷大）大于任何值。该值和数学意义上的无穷大很像，例如任何正值乘以 `Infinity` 为 `Infinity`, 任何数值（除了Infinity 和 -Infinity）除以 `Infinity` 为 0。

在 ECMAScript 5 的规范中， `Infinity` 是只读的（实现于 JavaScript 1.8.5 / Firefox 4）。

## 示例

    console.log(Infinity          ); /* Infinity */
    console.log(Infinity + 1      ); /* Infinity */
    console.log(Math.pow(10, 1000)); /* Infinity */
    console.log(Math.log(0)       ); /* -Infinity */
    console.log(1 / Infinity      ); /* 0 */

## 规范

Specification | Status | Comment
--- | --- | ---
ECMAScript 1st Edition (ECMA-262) | Standard | Initial definition. Implemented in JavaScript 1.3
ECMAScript 5.1 (ECMA-262) Infinity | Standard |
ECMAScript 2015 (6th Edition, ECMA-262) Infinity | Standard |
ECMAScript Latest Draft (ECMA-262) Infinity | 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) | (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

- `Number.NEGATIVE_INFINITY`
- `Number.POSITIVE_INFINITY`
- `Number.isFinite`