我們的志工尚未將本文翻譯為 正體中文 (繁體) 版本。加入我們,幫忙翻譯!
您也可以閱讀本文的 English (US) 版本。

The global isFinite() function determines whether the passed value is a finite number. If  needed, the parameter is first converted to a number.

Syntax

isFinite(testValue)

Parameters

testValue
The value to be tested for finiteness.

Return value

false if the argument is positive or negative Infinity or NaN; otherwise, true.

Description

isFinite is a top-level function and is not associated with any object.

You can use this function to determine whether a number is a finite number. The isFinite function examines the number in its argument. If the argument is NaN, positive infinity, or negative infinity, this method returns false; otherwise, it returns true.

Examples

isFinite(Infinity);  // false
isFinite(NaN);       // false
isFinite(-Infinity); // false

isFinite(0);         // true
isFinite(2e64);      // true
isFinite(910);       // true

isFinite(null);      // true, would've been false with the 
                     // more robust Number.isFinite(null)

isFinite('0');       // true, would've been false with the 
                     // more robust Number.isFinite("0")

Specifications

Specification Status Comment
ECMAScript 3rd Edition (ECMA-262) Standard Initial definition.
ECMAScript 5.1 (ECMA-262)
The definition of 'isFinite' in that specification.
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'isFinite' in that specification.
Standard  
ECMAScript Latest Draft (ECMA-262)
The definition of 'isFinite' in that specification.
Draft  

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung InternetNode.js
Basic supportChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes

Legend

Full support  
Full support

See also

文件標籤與貢獻者

標籤: 
最近更新: wbamberg,