How to get length number JavaScript? 6 Simple Steps

Getting the length of a number in JavaScript might sound simple, but there are several nuances and techniques to consider when working with different types of numbers.

Whether you’re a beginner or an experienced developer, this article will guide you through the process of obtaining the length of a number in JavaScript.

Let’s delve later on into the details step by step.

Why get length of number?

We might want to get the length of a number in JavaScript when we want to determine how many digits it contains.

Moreover, this can be useful in various scenarios such as formatting numbers for display or performing calculations based on the number’s magnitude.

Let’s see this example below:

function numberLength(number) {
  // Convert the number to a string
  var numberString = number.toString();
  // Get the length of the string
  var length = numberString.length;
  return length;

var num = 12345;
var len = numberLength(num);
console.log("Number of digits:", len); // Output: Number of digits: 5

In the given example, the numberlength function takes a number as input and converts it to string which uses the toString() method.

Then it retrieves the length of that string using the length property. As a result, it gives the number of digits in the original number.

How to get length of number in JavaScript?

There are several ways to calculate the length of a number in JavaScript. Here, we’ll discuss some commonly used methods:

1. Using the toString() Method

One of the most straightforward methods to determine the length of a number is by converting it into a string and then using the length property of strings.

This method is effective and easy to implement:

const number = 12345;
const numberString = number.toString();
const length = numberString.length;

console.log(`The length of the number is: ${length}`);

Converting the number to a string using the toString allows us to leverage the length property of strings, which provides the desired result.

2. Converting Number to String and Using length Property

Converting a number to a string and then utilizing the length property is a straightforward method to find its length.


function getNumberLength(number) {
    return number.toString().length;

const num = 9876;
const length = getNumberLength(num); // length will be 4

3. Handling Negative Numbers

For negative numbers, consider excluding the minus sign from the count.

function getNumberLength(number) {
    const numStr = number.toString();
    return numStr[0] === '-' ? numStr.length - 1 : numStr.length;

const num = -54321;
const length = getNumberLength(num); // length will be 5

4. Using Regular Expressions

Regular expressions offer a concise way to achieve this task. You can match all digits using a regular expression and calculate the count.


function getNumberLength(number) {
    return number.toString().match(/\d/g).length;

const num = 987654;
const length = getNumberLength(num); // length will be 6

5. Using the Math.log10() Function

The Math.log10() function is a powerful tool to determine the length of a positive number.

By taking the logarithm base 10 of the number and then adding 1, you can obtain the count of digits.

For example:

function getNumberLength(number) {
    return Math.floor(Math.log10(number)) + 1;

const num = 12345;
const length = getNumberLength(num); // length will be 5 

6. Iterative Division

Breaking down the number through iterative division is another technique.

function getNumberLength(number) {
    let count = 0;
    while (number !== 0) {
        number = Math.floor(number / 10);
    return count;
const num = 123;
const length = getNumberLength(num); // length will be 3


Calculating the length of a number in JavaScript might seem like a small task, but it has valuable applications in various programming scenarios.

By understanding the different methods available and their pros and cons, you’ll be well-equipped to handle number length calculations effectively.

Whether you’re validating user input, formatting numbers, or optimizing loop iterations, the knowledge gained from this guide will undoubtedly prove useful in your programming journey.

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