JavaScript (ES2026) reference · JSON and Global Functions

JavaScript isFinite() Function

Return true if a value is a finite number after converting it to a number. Prefer Number.isFinite() for strict checks.

JavaScript (ES2026) Since ES1

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Syntax

isFinite(value)

Parameter	Description
`value`	The value to test.

true or false.

Converts firstTry it yourself

console.log(isFinite(10), isFinite(Infinity), isFinite("10"));

Output

true false true

null converts to 0Try it yourself

console.log(isFinite(null), Number.isFinite(null));

Output

true false

Version	Change
JavaScript ES1	Added

Number.isFinite() · Return true if a value is a finite number. Unlike the global isFinite(), it doesn't convert strings.
isNaN() · Return true if a value is NaN after converting it to a number, so isNaN("hello") is true. Prefer Number.isNaN().
JavaScript Type Conversion · tutorial