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JavaScript isFinite() Function

JavaScript Global Functions


Definition and Usage

The isFinite() function is used to determine whether a parameter is infinite, or equivalently, whether it is a finite number.

Note: If the parameter is NaN, positive infinity, or negative infinity, it returns false; otherwise, it returns true.

Syntax

Parameter Description
value Required. The number to be tested.

Browser Support

Function
isFinite() Yes Yes Yes Yes Yes

Examples

Using isFinite() to test for infinite numbers:

document.write(isFinite(123) + "<br>");
document.write(isFinite(-1.23) + "<br>");
document.write(isFinite(5-2) + "<br>");
document.write(isFinite(0) + "<br>");
document.write(isFinite("Hello") + "<br>");
document.write(isFinite("2005/12/12") + "<br>");

The above example outputs:

true
true
true
true
false
false

More examples:

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

isFinite(0);         // true
isFinite(2e64);      // true, would be false in a stronger Number.isFinite(null)

isFinite("0");       // true, would be false in a stronger Number.isFinite('0')

JavaScript Global Functions

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