isFinite

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 2017 Draft (ECMA-262) The definition of 'isFinite' in that specification.	Draft

Browser compatibility

See also

• Number.isFinite()
• Number.NaN
• Number.POSITIVE_INFINITY
• Number.NEGATIVE_INFINITY