How to Replace All Underscore with Space in Javascript

In this tutorial, you will learn how to replace all underscore with space in javascript. A sentence is formed with the help of multiple words and these words are separated from each other with the help of a space. By having a space, not only the words but the entire sentence becomes meaningful.

Underscore (_) is a straight horizontal line drawn below text-level. You must have used or seen it in email addresses, filenames, URLs, etc. In case of URL, underscore is generally seen in URL path. However, these days Google recommends to use hyphen instead of underline.

There are numerous ways to replace all underscore with space. We are going to use the simplest approach which involves the usage of the regex pattern as well as replace() method. The replace() method searches the string for a particular value or a regex pattern and it returns a new string with the replaced values.

In the following example, we have one global variable that holds a string. Upon click of a button, we will replace all underscore with space and display the result on the screen.  Please have a look over the code example and the steps given below.


  • We have 3 elements in the HTML file (div, button, and h1). The div element is just a wrapper for the rest of the elements.
  • The innerText for the button element is “Replace”.
  • We have done some basic styling using CSS and added the link to our style.css stylesheet inside the head element.
  • We have also included our javascript file script.js with a script tag at the bottom.
<!DOCTYPE html>
<html lang="en">

  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <link rel="stylesheet" href="style.css">


  <div class="container">    

  <script src="script.js"></script>

.container {        
    text-align: center;

button {
  margin-top: 10px;
  padding: 10px 20px;


  • We have selected the button element and h1 element using the document.querySelector() method and stored them in btnReplace and output variables respectively.
  • We have attached a click event listener to the button element.
  • We have a global variable myString which holds a string as its value.
  • We are displaying the original string in the h1 element using the innerText property.
  • In the event handler function, we have regex variable that holds a regex pattern /_/g as its value.
  • We are calling replace() method and passing regex and space as parameters. As a result, it will replace all underscore with space. The new string returned by this method will be stored in the result variable.
  • We are displaying the result in the h1 element using the innerText property.
let btnReplace = document.querySelector("button");
let output = document.querySelector("h1");

let myString = "John is a very good_friend of mine and he likes playing_basketball.";

output.innerText = myString;

btnReplace.addEventListener("click", () => {
  let regex = /_/g;
  let result = myString.replace(regex, " ");
  output.innerText = result;