概述
Number.POSITIVE_INFINITY
属性表示正无穷大。
不必创建一个 Number
实例,可使用 Number.POSITIVE_INFINITY
来访问该静态属性。
Number.POSITIVE_INFINITY 属性的属性特性: |
|
---|---|
writable | false |
enumerable | false |
configurable | false |
描述
Number.POSITIVE_INFINITY
的值同全局对象 Infinity
属性的值相同。
该值的表现同数学上的无穷大有点儿不同:
- 任何正值,包括
POSITIVE_INFINITY
,乘以POSITIVE_INFINITY
为POSITIVE_INFINITY
。 - 任何负值,包括
NEGATIVE_INFINITY
,乘以POSITIVE_INFINITY
为NEGATIVE_INFINITY
。 - 0 乘以
POSITIVE_INFINITY
为 NaN。 - NaN 乘以
POSITIVE_INFINITY
为 NaN。 POSITIVE_INFINITY
除以NEGATIVE_INFINITY
以外的任何负值为NEGATIVE_INFINITY
。POSITIVE_INFINITY
除以POSITIVE_INFINITY
以外的任何正值为POSITIVE_INFINITY
。POSITIVE_INFINITY
除以NEGATIVE_INFINITY
或POSITIVE_INFINITY
为 NaN。- 任何数除以
POSITIVE_INFINITY
为 0。
You might use the Number.POSITIVE_INFINITY
property to indicate an error condition that returns a finite number in case of success. Note, however, that isFinite
would be more appropriate in such a case.
示例
下例中,赋值给变量 bigNumber
一个大于 JavaScript 中最大值的值。当 if
语句执行时,变量 bigNumber
值为 "Infinity
", 因此在继续执行代码前,为变量 bigNumber
设置一个容易管理的值。
var bigNumber = Number.MAX_VALUE * 2 if (bigNumber == Number.POSITIVE_INFINITY) { bigNumber = returnFinite(); }
规范
Specification | Status | Comment |
---|---|---|
ECMAScript 1st Edition. Implemented in JavaScript 1.1 | Standard | Initial definition. |
ECMAScript 5.1 (ECMA-262) Number.POSITIVE_INFINITY |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) Number.POSITIVE_INFINITY |
Standard |
浏览器兼容性
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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) |