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Using insertBefore in JavaScript DOM (Live Playground)

In this tutorial, we will learn how to use the insertBefore method in JavaScript to insert new HTML elements into the DOM at a specific position. We'll cover the basics of the insertBefore method and provide sample code with explanations.

What is insertBefore?​

The insertBefore method is a built-in JavaScript DOM method that allows you to insert a new HTML element into the DOM before a specified reference element. You can use the insertBefore method to create dynamic web pages by adding new content to the DOM in a specific order.

Sample Code: Using insertBefore​

Let's say we have the following HTML document:

<!DOCTYPE html>
<html>
  <head>
    <title>insertBefore Example</title>
  </head>
  <body>
    <div id="mainContainer">
      <h1 class="mainHeading">Welcome to My Web Page!</h1>
      <p class="mainParagraph" id="firstParagraph">This is an introductory paragraph.</p>
    </div>
  </body>
</html>

To use insertBefore to add a new HTML element to the DOM, you'll need to include a JavaScript <script> tag in your HTML document. For this example, we will add an inline script, although it's generally recommended to use external JavaScript files for larger projects.

Here's how you can create a new p element and insert it before the p element with the ID firstParagraph:

<!DOCTYPE html>
<html>
  <head>
    <title>insertBefore Example</title>
  </head>
  <body>
    <div id="mainContainer">
      <h1 class="mainHeading">Welcome to My Web Page!</h1>
      <p class="mainParagraph" id="firstParagraph">This is an introductory paragraph.</p>
    </div>

    <script>
      // Select the element with the ID "mainContainer" and "firstParagraph"
      var mainContainer = document.getElementById('mainContainer');
      var firstParagraph = document.getElementById('firstParagraph');

      // Create a new paragraph element
      var newParagraph = document.createElement('p');

      // Set the paragraph's attributes and text content
      newParagraph.textContent = 'This is a new paragraph.';
      newParagraph.setAttribute('id', 'newParagraph');
      newParagraph.setAttribute('class', 'newParagraphClass');

      // Insert the new paragraph element before the first paragraph using insertBefore
      mainContainer.insertBefore(newParagraph, firstParagraph);
    </script>
  </body>
</html>

After running this code, a new paragraph element with the ID newParagraph and the class newParagraphClass will be inserted before the p element with the ID firstParagraph.

Live Playground, Try it Yourself

Conclusion​

The insertBefore method is an essential tool for inserting HTML elements into the DOM at a specific position, allowing you to create dynamic and organized web pages. By mastering this method, you can create interactive and engaging web experiences that adapt to changing content needs and display your content in a precise order.