Math.log2()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

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

∀x>0,𝙼𝚊𝚝𝚑.𝚕𝚘𝚐𝟸(𝚡)=log2(x)=the unique y such that 2y=x\forall x > 0,\;\mathtt{\operatorname{Math.log2}(x)} = \log_2(x) = \text{the unique } y \text{ such that } 2^y = x

Try it

Syntax

js
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 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 Math.LOG2E, which is 1 / Math.LN2.

Examples

Using Math.log2()

js
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

Specification
ECMAScript Language Specification
# sec-math.log2

Browser compatibility

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See also