isFinite()

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

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Syntax

js

isFinite(testValue)

Parameters

testValue

The value to be tested for finiteness.

Return value

false if the argument is (or will be coerced to) positive or negative Infinity or NaN or undefined; otherwise, true.

Description

isFinite is a function property of the global 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

Using isFinite

js

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

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

// Would've been false with the more robust Number.isFinite():
isFinite(null); // true
isFinite("0"); // true

Specifications

Specification
ECMAScript Language Specification
# sec-isfinite-number

Browser compatibility

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See also