# How to Use the Math.log() Method in JavaScript

09/30/2021

Contents

In this article, you will learn how to use the Math.log() method in JavaScript.

## Using the Math.log() method in JavaScript

The Math.log() method is a built-in function in JavaScript that returns the natural logarithm (base e) of a given number. The input parameter must be a positive number.

### Syntax

The syntax for using the Math.log() method is:

``Math.log(x)``

where x is the input parameter that represents the number to calculate the natural logarithm of.

### Examples

#### Using Math.log() to calculate the natural logarithm of a number

``````const x = 5;
const naturalLogarithm = Math.log(x);
console.log(naturalLogarithm); // 1.6094379124341003
``````

In this example, the input parameter is 5. The output is the natural logarithm (base e) of 5, which is approximately 1.6094.

#### Using Math.log() with a value less than or equal to 0

``````const x = -2;
const naturalLogarithm = Math.log(x);
console.log(naturalLogarithm); // NaN
``````

In this example, the input parameter is -2, which is less than or equal to 0. Therefore, the output is NaN.

#### Using Math.log() with a value greater than 0

``````const x = 0.2;
const naturalLogarithm = Math.log(x);
console.log(naturalLogarithm); // -1.6094379124341003
``````

In this example, the input parameter is 0.2. The output is the natural logarithm (base e) of 0.2, which is approximately -1.6094.

Note: If you want to calculate the logarithm of a number using a different base, you can use the following formula:

``logb(x) = Math.log(x) / Math.log(b)``

where x is the number to calculate the logarithm of, and b is the desired base.