Explain Event Bubbling and Capturing in JavaScript | Javascript Interview Questions and Answers

Question : Explain Event Bubbling and Capturing in JavaScript?

Answer : Event bubbling and event capturing are two mechanisms in JavaScript for handling events that occur on DOM elements, especially in the context of event propagation.

1. **Event Capturing**:
- In event capturing, when an event is triggered on a nested element, it starts from the outermost element in the DOM hierarchy and propagates down to the target element.
- The browser captures the event during the downward phase before it reaches the target element.
- Event capturing is specified as the third parameter of the `addEventListener()` method, where you pass `true` to enable it.

```javascript
```

- Event capturing allows you to intercept events at a higher level in the DOM hierarchy before they reach the target element. It's less commonly used compared to event bubbling.

2. **Event Bubbling**:
- In event bubbling, when an event is triggered on a nested element, it starts from the target element and propagates upwards through its ancestors in the DOM hierarchy.
- The event bubbles up through the DOM tree until it reaches the outermost element.
- Event bubbling is the default behavior in most browsers.
- You can enable event bubbling explicitly by passing `false` or omitting the third parameter of the `addEventListener()` method (since `false` is the default value).

```javascript
```

- Event bubbling allows you to handle events at a higher level in the DOM hierarchy after they have bubbled up from the target element. It's more commonly used in event handling.

Here's a visual representation of event propagation:

```
+-------------------------------------------+
| +---------------------------------+ |
| | +-------------------------+ | |
| | | | | |
| | | Target | | |
| | | | | |
| | +-------------------------+ | |
| | | | |
| | | | |
| | +-------------------------+ | |
| | | | | |
| | | Ancestor Element | | |
| | | | | |
| | +-------------------------+ | |
| | | | |
| | | | |
| | +-------------------------+ | |
| | | | | |
| | | Outermost Element | | |
| | | | | |
| | +-------------------------+ | |
| +---------------------------------+ |
+-------------------------------------------+
```

Understanding event bubbling and capturing is important for building robust and efficient event handling systems in web applications. Depending on the requirements, you can choose either event capturing or event bubbling or both to handle events effectively.

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