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Javascript in 100 bits

Course by zooboole,

Last Updated on 2025-01-28 08:04:00

Lesson 43 - Modifying Elements in the DOM

This lesson focuses on modifying HTML elements using JavaScript. You will learn how to change text content, update attributes, and modify styles dynamically.

1. Changing Text Content

Use .textContent or .innerHTML to change the content of an element.

Example 1: Changing Text with textContent

document.getElementById("message").textContent = "Hello, JavaScript!";
  • Updates the text inside the element without interpreting HTML.

Example 2: Changing Text with innerHTML

document.getElementById("message").innerHTML = "<strong>Bold Text</strong>";
  • Parses HTML, so <strong> is rendered as bold.

2. Changing Element Attributes

Modify attributes like src, href, alt, etc., using .setAttribute() or direct property manipulation.

Example 1: Updating Image Source

document.getElementById("myImage").src = "new-image.jpg";

Example 2: Updating Link URL

document.getElementById("myLink").href = "https://lancecourse.com";

3. Changing CSS Styles

Use .style.property or .classList to modify styles dynamically.

Example 1: Changing Color with .style

document.getElementById("title").style.color = "blue";

Example 2: Adding and Removing CSS Classes

document.getElementById("box").classList.add("highlight"); // Add a class
document.getElementById("box").classList.remove("hidden"); // Remove a class

Try Your Hand

Steps:

  1. Create a File: Name it lesson43-modifying-elements.html

  2. Write the Code:

    <!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>Lesson 43 - Modifying Elements</title>
   <style>
       .highlight { color: red; font-weight: bold; }
   </style>
</head>
<body>
   <h2 id="title">Modify This Text</h2>
   <button onclick="changeText()">Change Text</button>
   <button onclick="changeColor()">Change Color</button>

   <script>
       function changeText() {
           document.getElementById("title").textContent = "Text Changed!";
       }
       function changeColor() {
           document.getElementById("title").classList.toggle("highlight");
       }
   </script>
</body>
</html>
  3. Save and Open in a Browser to see dynamic text and style updates.

Key Takeaways

  • .textContent modifies text without parsing HTML.
  • .innerHTML modifies text and parses HTML.
  • .setAttribute() changes element attributes.
  • .style.property modifies styles dynamically.
  • .classList helps add, remove, or toggle classes.