What is JavaScript event delegation

JavaScript event delegation is a technique used to handle events in a more efficient and maintainable way. Instead of attaching an event listener to each individual element that needs to respond to an event, event delegation allows you to attach a single event listener to a parent element and then use logic to determine which child element should handle the event.

The idea behind event delegation is that events bubble up the DOM tree, which means that when an event is triggered on a child element, it will also be triggered on all of its parent elements. By attaching an event listener to a parent element, you can take advantage of this behavior to handle events on multiple child elements at once.

Here is an example of how to use event delegation:

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

<script>
  document.getElementById("list").addEventListener("click", function(event) {
    if (event.target.tagName === "LI") {
      console.log("List item clicked: " + event.target.textContent);
    }
  });
</script>

In this example, an event listener is attached to the parent ul element, and when a click event is fired, the event is handled by the callback function. Inside the callback function, we use the event.target property to check the type of the element that was actually clicked. If it is an LI element, we can display the text of the clicked element in the console.

Event delegation is useful in situations where the structure of the page is dynamic and elements are added or removed dynamically, so it is not possible to attach event listeners to all elements before they are added. It also can be useful in situations where you have many elements that need to respond to the same event, as it can reduce the number of event listeners and improve the performance of your code.

In summary, event delegation is a technique that allows you to handle events on multiple elements by attaching a single event listener to a parent element, and then using logic to determine which child element should handle the event. It can help to improve the performance and maintainability of your code in certain situations.

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