isFinite() - JavaScript 编辑

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

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

Syntax

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

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

Browser compatibility

BCD tables only load in the browser

See also

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