Changing Template Colors with JavaScript: A Guide to Dynamic Color Customization

Changing template colors in JavaScript refers to the ability to dynamically modify the color scheme of a web page or application using JavaScript. This is a common feature in web development that allows users to personalize the visual appearance of a website or web app to suit their preferences.

Color Customization Elements : To enable color customization, you typically provide UI elements, such as color pickers or theme selectors, that users can interact with to choose different colors for various parts of the template, such as backgrounds, text, buttons, links, and more.

JavaScript DOM Manipulation : JavaScript is used to manipulate the Document Object Model (DOM) of the web page dynamically. It can target specific HTML elements and apply CSS styles to them. In the context of color customization, JavaScript is responsible for changing the values of CSS properties that control colors.

CSS Variables or Classes : There are two common approaches to implementing color customization:

  • CSS Variables (Custom Properties): CSS custom properties, also known as CSS variables, allow you to define variables in CSS to represent colors. JavaScript can then change the values of these variables, which will automatically update the styles throughout the page.
  • CSS Classes: You can define CSS classes for different color schemes, and JavaScript can toggle or switch between these classes to apply different color styles.

Event Handling : Event listeners are used to detect user interactions with color customization UI elements. When a user selects a color or theme, JavaScript captures this interaction and updates the styles accordingly.

Storing User Preference : To ensure that users' color preferences are remembered between visits or page reloads, you may store their choices in a user's browser, often using techniques like Local Storage or cookies.

Accessibility Considerations : It's crucial to consider accessibility when implementing color customization. Ensure that the chosen colors maintain sufficient contrast and readability, and provide options for users with different visual needs.

To enhance the user experience, it's essential to add CSS styles to the HTML page for a visually appealing and organized presentation of content.

sample Code

<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Dark Light</title>
    <link rel="stylesheet" href="style.css" />
    <div class="banner" id="banner">
      <h1 class="title">Welcome to Tutor Joe's</h1>
      <p class="slogan">Discover the possibilities</p>
      <button id="theme-toggle">Toggle Theme</button>
    <script src="script.js"></script>

<div> Element with Class and ID

  • The <div> element is a generic container used to group and structure content on a web page.
  • class="banner" and id="banner": These attributes assign a CSS class ("banner") and a unique identifier ("banner") to the <div>. CSS classes and IDs are commonly used to style and select elements using CSS and JavaScript.

<h1> Element

  • The <h1> element represents the main heading of the webpage.
  • class="title": This attribute assigns a CSS class ("title") to the <h1>. It can be used for styling with CSS.

<p> Element:

  • The <p> element represents a paragraph of text.
  • class="slogan": This attribute assigns a CSS class ("slogan") to the <p>. Like the title, it can be styled with CSS.

<button> Element:

  • The <button> element creates a clickable button on the webpage.
  • id="theme-toggle": This attribute assigns a unique identifier ("theme-toggle") to the button, which can be used to select the button using JavaScript.

Text Content

  • Inside the <h1> element, you have the text "Welcome to Tutor Joe's," which is the main title of the webpage.
  • Inside the <p> element, you have the text "Discover the possibilities," which serves as a slogan or tagline.
  • Inside the <button> element, you have the text "Toggle Theme," which represents the label of the button that users can click.

Overall, this HTML code represents a banner section at the top of a webpage. It includes a title, a slogan, and a button that can be used to toggle between different themes or perform some other action when clicked. To implement theme toggling or any other interactivity, you would typically use JavaScript and CSS in conjunction with this HTML structure.


const btnToggle = document.getElementById("theme-toggle");

function toggleTheme() {
  const banner = document.getElementById("banner");

  const isDarkTheme = banner.classList.contains("dark");

  localStorage.setItem("themePreference", isDarkTheme ? "dark" : "light");

btnToggle.addEventListener("click", toggleTheme);

window.addEventListener("DOMContentLoaded", function () {
  const themePreference = localStorage.getItem("themePreference");
  if (themePreference === "dark") {
    const banner = document.getElementById("banner");

This JavaScript code provides functionality to toggle between a light and dark theme for a webpage using a button click and to remember the user's theme preference using Local Storage.

const btnToggle = document.getElementById("theme-toggle");: This line selects the button with the id "theme-toggle" and assigns it to the btnToggle variable. This button is used to toggle the theme.

function toggleTheme() { ... }: This is a function that handles toggling between the light and dark themes. It does the following:

  • It selects the element with the id "banner," which is assumed to be the container for the content you want to apply the theme to.
  • It uses the classList.toggle() method to toggle the "dark" class on the "banner" element, effectively switching between light and dark themes.
  • It checks if the "dark" class is present on the "banner" element to determine whether the dark theme is currently active.
  • It stores the user's theme preference ("dark" or "light") in Local Storage using localStorage.setItem().

btnToggle.addEventListener("click", toggleTheme);: This line adds a click event listener to the "Toggle Theme" button. When the button is clicked, it triggers the toggleTheme function to switch the theme.

window.addEventListener("DOMContentLoaded", function () { ... });: This is an event listener that waits for the DOM (webpage) to be fully loaded before executing its code. Inside this event listener:

  • It retrieves the user's theme preference from Local Storage using localStorage.getItem().
  • It checks if the user prefers a dark theme. If the user previously selected a dark theme, it adds the "dark" class to the "banner" element to apply the dark theme immediately upon page load.

Overall, this code provides a simple mechanism to allow users to toggle between light and dark themes on a webpage and remembers their preference across page visits using Local Storage.


@import url(";400;500;600;700&display=swap");

* {
  font-family: "Poppins", sans-serif;

.banner {
  background-color: #f1e9e9;
  color: #446456;
  padding: 20px;

.title {
  font-size: 28px;
  font-weight: 500;
  margin: 0;

.slogan {
  font-size: 18px;

.dark {
  background-color: #333333;
  color: #ffffff;

List of Programs

JS Practical Questions & Answers

JS Practical Project