What is the difference between event.preventDefault() and event.stopPropagation() in JavaScript?

[ir3ne]

[travisliu]

Understanding the Difference Between event.preventDefault() and event.stopPropagation() in JavaScript

JavaScript is used to make websites interactive, and it often has to respond to different actions a user takes, like clicking a button or filling out a form. To do this, JavaScript listens to "events" on a webpage, and sometimes developers use special commands to control these events. Two of those commands are event.preventDefault() and event.stopPropagation(). Although they sound similar, they do different things. Let's explore each one!

What Does event.preventDefault() Do?

event.preventDefault() is used when you want to stop the browser from doing something that it would normally do. For example, when you click on a link, the browser usually takes you to a new webpage. But sometimes, you might want to stop this from happening. Imagine you click on a link, but instead of going to a new page, you want a pop-up message to show. This is where event.preventDefault() comes in.

Here are a few examples of when you might use event.preventDefault():

• Stopping a link from opening a new webpage.
• Preventing a form from being submitted before all the fields are filled out.

In short, event.preventDefault() blocks the browser's default behavior for an event.

What Does event.stopPropagation() Do?

event.stopPropagation() is used when you want to stop an event from "bubbling" up to other elements. Let me explain what "bubbling" means. In HTML, elements are often nested inside each other. For instance, a button might be inside a div, and that div might be inside a larger section. When you click on the button, JavaScript sees that click event not only on the button but also on all the elements around it, like the div and the section. This process is called "event bubbling."

Sometimes, you want to stop this bubbling. For example, if you click on a button, you may want only the button to react, not the whole page. By using event.stopPropagation(), you can make sure that the event stays only with the button and doesn't affect the other elements.

Here are a few examples of when you might use event.stopPropagation():

• Preventing a click on a button from also triggering a click event on its parent element.
• Making sure only one specific part of the page reacts to an event without affecting other parts.

In short, event.stopPropagation() stops an event from spreading out to other elements.

Summary: The Key Difference

• event.preventDefault() stops the browser’s default action for an event. It’s like telling the browser, "Don’t do what you usually do!"
• event.stopPropagation() stops an event from moving up the chain of elements. It’s like telling the event, "Stay here, don’t tell anyone else!"

Knowing the difference between these two commands can help you better control how your webpage behaves, making it more interactive and user-friendly!

[ir3ne]

Thanks @travisliu! Could you open a PR for this?