JavaScript - global isFinite() vs Number.isFinite()

In this short article, we would like to show comparision between global isFinite() vs Number.isFinite() methods in JavaScript.

Quick solution:

Global isFinite() method first converts value to number, that causes returning true for:

• null,
• boolean values,
• empty strings
• number strings,
• etc.

Number.isFinite() method doesn't.

Simple summary: 

Hint: check practical examples for more cases.

Practical examples

In this section you can find runnable examples that shows isFinite() methods results.

Global isFinite() method

// ONLINE-RUNNER:browser;

console.log(isFinite(1000));       // true
console.log(isFinite(3.14));       // true

console.log(isFinite(true));       // true
console.log(isFinite(false));      // true

console.log(isFinite(NaN));        // false
console.log(isFinite(Infinity));   // false
console.log(isFinite(null));       // true
console.log(isFinite(undefined));  // false

console.log(isFinite('1000'));     // true
console.log(isFinite('3.14'));     // true


// Crazy case:

console.log(isFinite([]));         // true
console.log(isFinite([1000]));     // true
console.log(isFinite(['ab']));     // false

Number.isFinite() method

// ONLINE-RUNNER:browser;

console.log(Number.isFinite(1000));       // true
console.log(Number.isFinite(3.14));       // true

console.log(Number.isFinite(true));       // false
console.log(Number.isFinite(false));      // false

console.log(Number.isFinite(NaN));        // false
console.log(Number.isFinite(Infinity));   // false
console.log(Number.isFinite(null));       // false
console.log(Number.isFinite(undefined));  // false

console.log(Number.isFinite('1000'));     // false
console.log(Number.isFinite('3.14'));     // false


// Crazy case:

console.log(Number.isFinite([]));         // false
console.log(Number.isFinite([1000]));     // false
console.log(Number.isFinite(['ab']));     // false