Number.isFinite()

Number.isFinite() 方法會判斷傳入的值是否為有限數(finite number)。

語法

Number.isFinite(value)

參數

value
The value to be tested for finiteness.

回傳值

A Boolean indicating whether or not the given value is a finite number.

說明

In comparison to the global isFinite() function, this method doesn't forcibly convert the parameter to a number. This means only values of the type number, that are also finite, return true.

範例

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

Number.isFinite(0);         // true
Number.isFinite(2e64);      // true

Number.isFinite('0');       // false, would've been true with
                            // global isFinite('0')
Number.isFinite(null);      // false, would've been true with
                            // global isFinite(null)

Polyfill

Number.isFinite = Number.isFinite || function(value) {
    return typeof value === 'number' && isFinite(value);
}

規範

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Number.isInteger' in that specification.
Standard Initial definition.
ECMAScript (ECMA-262)
The definition of 'Number.isInteger' in that specification.
Living Standard  

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