Add a Simple Dark Mode Toggle with HTML, CSS, and JavaScript

Quick Guide to Building a Simple Dark Mode Feature

Follow these steps to create a basic dark mode toggle switch using HTML, CSS, and JavaScript. This implementation also saves the user’s theme preference with localStorage, so the dark mode persists across sessions.

preview:

Step1: create index.html . you can copy the html file from my github

. Start by setting up a simple HTML structure. You can also find this code on my GitHub. Here’s the main toggle button:

index.html
`

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

Step 2: Style the Dark Mode Toggle with CSS

Define the base styles for the toggle switch and the circle indicator:

#dark{

display: inline-block;

width: 50px;

border: 1px  solid  #f0cff0;

border-radius: 25px;

}

#circle{

width: 20px;

height: 20px;

border-radius: 100%;

background-color: #ffcc00;

}

Now, create additional classes to toggle the circle position and apply

dark mode styling:
.toggle{
 margin-left: 50%;

}

.dark_mode{
 background: #252526  !important;
 color: #fff;

}

Step 3: JavaScript for Theme Persistence

const  circle  =  document.getElementById("circle");
const  dark_button=  document.getElementById("dark")
const  body  =  document.getElementById("_body")

*Step 4: Understand the Theme Handling Logic
*

Here if theme key/variable === dark we’ll run darkMode function other wise we’ll execute lightMode function

Step 5: Create the Dark and Light Mode Functions

Define the functions to add or remove dark mode styling based on the theme setting:

const  theme  =  localStorage.getItem("theme")
theme  ===  "dark"  ?  darkMode() :  lightMode();

 function darkMode() {

     body.classList.add("dark_mode")
     circle.classList.add("toggle")
     circle.style.background = "#E2EAF4";

     localStorage.setItem("theme", "dark")
}

function lightMode() {

  body.classList.remove("dark_mode");
  circle.classList.remove("toggle")
  circle.style.background = "#524b38";
  localStorage.setItem("theme", "light")

}

Step 6: Add Toggle Functionality to the Button

Finally, set up an event listener on the button to switch themes and update localStorage:

dark_button.addEventListener("click", () => {

circle.classList.toggle("toggle");

if (circle.classList.contains("toggle")) {

localStorage.setItem("theme", "dark")

}else{

localStorage.setItem("theme", "light")

}

  const  theme  =  localStorage.getItem("theme")

theme  ===  "dark"  ?  darkMode() :  lightMode()

})

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