files/en-us/web/javascript/reference/global_objects/math/log2/index.md

metadata

title: Math.log2()
short-title: log2()
slug: Web/JavaScript/Reference/Global_Objects/Math/log2
page-type: javascript-static-method
browser-compat: javascript.builtins.Math.log2
sidebar: jsref

The Math.log2() static method returns the base 2 logarithm of a number. That is

$$\forall x>0,𝙼𝚊𝚝𝚑.𝚕𝚘𝚐𝟸(𝚡)={log}_2(x)=\text{the unique }y\text{ such that }{2}^y=x\backslash forall\; x\; >\; 0,\backslash ;\backslash mathtt\{\backslash operatorname\{Math.log2\}(x)\}\; =\; \backslash log\_2(x)\; =\; \backslash text\{the\; unique\; \}\; y\; \backslash text\{\; such\; that\; \}\; 2^y\; =\; x$$

{{InteractiveExample("JavaScript Demo: Math.log2()")}}

console.log(Math.log2(3));
// Expected output: 1.584962500721156

console.log(Math.log2(2));
// Expected output: 1

console.log(Math.log2(1));
// Expected output: 0

console.log(Math.log2(0));
// Expected output: -Infinity

Syntax

Math.log2(x)

Parameters

• x
  • : A number greater than or equal to 0.

Return value

The base 2 logarithm of x. If x < 0, returns {{jsxref("NaN")}}.

Description

Because log2() is a static method of Math, you always use it as Math.log2(), rather than as a method of a Math object you created (Math is not a constructor).

This function is the equivalent of Math.log(x) / Math.log(2). For log2(e), use the constant {{jsxref("Math.LOG2E")}}, which is 1 / {{jsxref("Math.LN2")}}.

Examples

Using Math.log2()

Math.log2(-2); // NaN
Math.log2(-0); // -Infinity
Math.log2(0); // -Infinity
Math.log2(1); // 0
Math.log2(2); // 1
Math.log2(3); // 1.584962500721156
Math.log2(1024); // 10
Math.log2(Infinity); // Infinity

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• Polyfill of Math.log2 in core-js
• {{jsxref("Math.exp()")}}
• {{jsxref("Math.log()")}}
• {{jsxref("Math.log10()")}}
• {{jsxref("Math.log1p()")}}
• {{jsxref("Math.pow()")}}