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Event Delegation in JavaScript DOM Events (Live Playground)

Event delegation is a technique that takes advantage of event propagation to handle events more efficiently and with less code. In this tutorial, we will learn about event delegation, its benefits, and how to implement it in your JavaScript DOM event handling.

What is Event Delegation?​

Event delegation involves attaching a single event listener to a parent element, instead of attaching multiple event listeners to each child element. The event listener on the parent element listens for events bubbling up from its child elements and handles them accordingly.

Benefits of Event Delegation​

  1. Performance: Attaching a single event listener to a parent element consumes less memory and improves the performance of your web application.
  2. Dynamic Elements: Event delegation works seamlessly with elements that are dynamically added or removed from the DOM, without the need to reattach event listeners.
  3. Code Maintainability: Event delegation reduces the amount of code required to handle events, making your codebase easier to understand and maintain.

Implementing Event Delegation​

Let's consider a simple example to understand how event delegation works. Suppose we have a list with multiple items and we want to log the text of the clicked item.

<ul id="itemList">
  <li>Item 1</li>
  <li>Item 2</li>
  <li>Item 3</li>
  <li>Item 4</li>
</ul>

Instead of attaching an event listener to each <li> element, we attach a single event listener to the parent <ul> element.

const itemList = document.getElementById('itemList');

itemList.addEventListener('click', event => {
  const clickedElement = event.target;

  if (clickedElement.tagName === 'LI') {
    console.log('Clicked item:', clickedElement.textContent);
  }
});

In this example, the event listener is attached to the itemList element. When an <li> element is clicked, the event bubbles up to the itemList, where it is captured by the event listener. The event listener checks if the clicked element is an <li> and logs its text content if it is.

Live Playground, Try it Yourself

Conclusion​

In this tutorial, we've learned about event delegation and how to implement it in JavaScript DOM event handling. By using event delegation, you can improve the performance and manageability of your web applications, especially when dealing with a large number of elements or dynamic content.