How to implement Dark Mode in JavaScript

How to implement Dark Mode in JavaScript

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Hello, my gorgeous friends on the internet ๐Ÿ˜,

In this article, you will learn how to implement dark mode in JavaScript, I implemented this feature in one of my coming articles, so I think of extracting it for you guys ๐Ÿ˜Ž, you can check out what we will be building HERE before you continue reading.


I assume you have worked with HTML, CSS, JavaScript functions and understand DOM a little bit, we actually do not need much ๐Ÿ˜.

Without any further ado, let's get started

tom running on a spot at the start line, funny

This article will be split into 3 parts

  1. HTML
  2. CSS


Don't worry much about the markup, go ahead and copy-paste the code below ๐Ÿ‘‡

<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <!-- Bootstrap -->
    <link rel="stylesheet" href="./index.css" />
    <title>Dark Mode Switcher</title>
    <main class="blog container">
      <div class="content">
        <!-- Mode switch -->
        <section class="mode-switch">
          <div class="form-check form-switch">
              class="form-check-input shadow-none"
            <label class="form-check-label" for="toggle-btn"
              >Toggle Dark Mode</label
        <!-- Article section -->
        <section class="article-section">
            <h1 class="article-heading">
              How to implement Dark Mode in JavaScript
            <span class="read-time text-muted">2 min read</span>
            <p class="article-body">
              Hello ๐Ÿ‘‹, my gorgeous friend on the internet ๐Ÿ˜
              <br />
              Before we continue, you have to switch to dark mode ๐Ÿ‘†. Now switch
              back and that is what we will build together in
              <a href="http://" target="_blank" rel="noopener noreferrer"
              <br />
            <h3 class="article-sub--heading">History Of Lorem</h3>
            <p class="article-body">
              Lorem Ipsum is simply dummy text of the printing and typesetting
              industry. Lorem Ipsum has been the industry's standard dummy text
              ever since the 1500s, when an unknown printer took a galley of
              type and scrambled it to make a type specimen book. It has
              survived not only five centuries, but also the leap into
              electronic typesetting, remaining essentially unchanged. It was
              popularised in the 1960s with the release of Letraset sheets
              containing Lorem Ipsum passages, and more recently with desktop
              publishing software like Aldus PageMaker including versions of
              Lorem Ipsum.
            <h3 class="article-sub--heading">Why do we need Lorem</h3>
            <p class="article-body">
              It is a long established fact that a reader will be distracted by
              the readable content of a page when looking at its layout. The
              point of using Lorem Ipsum is that it has a more-or-less normal
              distribution of letters, as opposed to using 'Content here,
              content here', making it look like readable English. Many desktop
              publishing packages and web page editors now use Lorem Ipsum as
              their default model text, and a search for 'lorem ipsum' will
              uncover many web sites still in their infancy. Various versions
              have evolved over the years, sometimes by accident, sometimes on
              purpose (injected humour and the like).
    <script src="./index.js"></script>
  • If all goes well, your browser output should look something like this ๐Ÿ‘‡

blog page with pure html


Copy-paste the CSS styles below ๐Ÿ‘‡

@import url(",wght@0,200;0,300;0,400;0,500;0,600;0,700;0,900;1,200;1,300;1,400;1,500;1,600;1,800;1,900&display=swap");

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
  font-family: "Poppins";

#toggle-btn {
  cursor: pointer;

.blog {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  min-height: 60vh;

main .content {
  max-width: 90%;

.mode-switch {
  margin: 2rem 0;

.article-heading {
  text-transform: uppercase;
  margin-top: 2.5rem;

.article-sub--heading {
  margin-top: 2rem;

.article-body {
  margin-top: 1rem;
  line-height: 2;

/* DARK MODE */ {
  transition: 0.9 all ease;
  background-color: #202124;

.dark .content {
  color: #fdfdfd;

.dark .article-heading {
  font-weight: 800;

.dark .article-sub--heading {
  font-weight: 700;

@media (min-width: 900px) {
  main .content {
    max-width: 70%;
  • Your browser output should look like this ๐Ÿ‘‡

 blog page output with css styles


What we just did under the hood in the CSS PART is that we declared a style rule for our dark mode version, which we are going to be using later.

Dark Mode Version Style ๐Ÿ‘‡

/* DARK MODE */ {
  transition: 0.9 all ease;
  background-color: #202124;

.dark .content {
  color: #fdfdfd;

.dark .article-heading {
  font-weight: 800;

.dark .article-sub--heading {
  font-weight: 700;
  • To test this manually add dark to the main tag class attribute like below ๐Ÿ‘‡

Manually Add dark mode class.png

  • You should have the dark mode displayed like below ๐Ÿ‘‡

manual dark mode out put

  • You should notice that the dark mode is having a more bold heading, you can specify more styles to define how you want the dark mode to look with the dark selector (don't forget the visibility of elements when styling dark-mode).

  • But this class will not be inserted into our HTML manually, we can't do that for each of our users, so remove it and let's proceed to use JavaScript.


Here is where the real work is, now that we know the class (dark) to inject into our HTML main tag, let us proceed to use JavaScript to automate the theme switching.

Copy Paste the code below ๐Ÿ‘‡

// DOM
const blogContainer = document.querySelector(".blog");
const toggleButton = document.querySelector("#toggle-btn");

// Function to switch the theme
const switchTheme = () => {

// Bind event to the toggle button
toggleButton.addEventListener("click", switchTheme);


In order to achieve the switching of theme, we need to do the following ๐Ÿ‘‡

  1. Get access to the element (main) which we need JavaScript to inject the dark class into. ``` const blogContainer = document.querySelector(".blog");

- Have access to the switch button so we can bind a function into it later.

const toggleButton = document.querySelector("#toggle-btn");

- Create a function that will handle the action of toggling (switching) the *dark* class name inside the main tag

const switchTheme = () => { blogContainer.classList.toggle("dark"); };

- Finally, we need to bind the function to the switch button with an `eventListener`

toggleButton.addEventListener("click", switchTheme);


And that is it for this article,


You can try to implement a feature where your site remembers the last theme of the user, let me know if you need help in the comment section.

Wow, what a journey, I am glad you made it to the end of this article, if you enjoyed and learned from this article, I will like to connect with you.

Let's connect on

My friend and I are holding a meetup every Saturday to discuss JavaScript and other programming tips and to support ourselves.

You can be a part ๐Ÿ‘‡ of the community by joining our WhatsApp group

See you in the next article. Bye Bye ๐Ÿ™‹โ€โ™‚๏ธ


If you found this helpful and want to support my blog, you can also buy me a coffee below.