JavaScript Number.isFinite()Method

Number 对象参考手册JavaScript Number Object

Example

Check whether the parameter is infinite:

Number.isFinite(123) //true Number.isFinite(-1.23) //true Number.isFinite(5-2) //true Number.isFinite(0) //true Number.isFinite('123') //false Number.isFinite('Hello') //false Number.isFinite('2005/12/12') //false Number.isFinite(Infinity) //false Number.isFinite(-Infinity) //false Number.isFinite(0 / 0) //false

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Definition and Usage

Number.isFinite() is a built-in method in JavaScript used to determine whether a value is a finite number (that is, whether it is a normal number, rather than Infinity, -Infinity, or NaN).

isFinite() is part of the Number object, used to ensure that a value is a valid, finite numeric type.

Note:If number is NaN (Not-a-Number), or is positive or negative infinity, it returns false.

Number.isFinite() differs from the globalisFinite()function,Number.isFinite()it does not perform type conversion, but strictly checksvaluewhether the value is a finite number. In contrast,isFinite()the method first converts its parameter to a number and then makes the judgment.

1. Basic Usage

Example

console.log(Number.isFinite(2));        // true: 2 is a finite number
console.log(Number.isFinite(3.14));     // true: 3.14 is a finite number
console.log(Number.isFinite(-100));     // true: -100 is a finite number
console.log(Number.isFinite(1 / 0));    // false: Infinity is not a finite number
console.log(Number.isFinite(-1 / 0));   // false: -Infinity is not a finite number
console.log(Number.isFinite(NaN));      // false: NaN is not a finite number
console.log(Number.isFinite('2'));      // false: '2' is a string, not a number

2、Number.isFinite() vs isFinite()

Example

console.log(isFinite(2));         // true: global isFinite performs type conversion
console.log(isFinite('2'));       // true: string '2' is converted to number 2
console.log(Number.isFinite(2));  // true: 2 is a finite number
console.log(Number.isFinite('2'));// false: string '2' is not a numeric type

3. NaN and Infinity

Example

console.log(Number.isFinite(NaN));       // false: NaN is not a finite number
console.log(Number.isFinite(Infinity));  // false: Infinity is not a finite number
console.log(Number.isFinite(-Infinity)); // false: -Infinity is not a finite number

4. Type Conversion

Number.isFinite() does not automatically convert the passed value to a number, so it is strict in its judgment. For values of other types, it directly returns false.

Example

console.log(Number.isFinite(true));     // false: boolean true is not a number
console.log(Number.isFinite(undefined)); // false: undefined is not a number
console.log(Number.isFinite(null));     // false: null is not a number

Browser Support

Method
Number.isFinite() 19 12.0 16 9 22

Syntax

Number.isFinite(value)

Parameter Values

Parameter Description
value The value to be checked, can be data of any type (e.g., number, string, object, boolean, etc.).

Return Value

Type Description
Boolean Returns true if value is a finite number.
Returns false if value is not a finite number (e.g., NaN, Infinity, -Infinity, or a non-number type).

Technical Details

JavaScript Version: ECMAScript 6

Number 对象参考手册JavaScript Number Object

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