Explain the concept of "event bubbling" in JavaScript.

@genoveva.langosh 

"Event bubbling" is a concept in JavaScript that describes how events propagate or bubble up through the DOM (Document Object Model) hierarchy. When an event is triggered on a DOM element, such as a click event on a button, the event is first captured by the element that received the event. Then, the event travels up through the ancestor elements of the DOM tree until it reaches the top-level element, which is typically the document object.

During this process, the event triggers any event listeners that have been registered on each of the elements in the path of the event. This can be useful because it allows a single event handler to be registered on a parent element, which will handle events triggered by any of its descendant elements. This is known as "event delegation" and can help to improve the performance of web applications by reducing the number of event listeners that need to be registered.

However, it's important to be aware of event bubbling when designing event handlers, as it can cause unexpected behavior if not handled properly. For example, if you have nested elements with event listeners, you may end up triggering the event listener on both the child and parent elements, leading to unintended consequences. To prevent this, you can use the stopPropagation() method to stop the event from bubbling up the DOM tree.

Overall, understanding event bubbling is important for creating efficient and effective event handlers in JavaScript, and can help to optimize the performance of web applications.