event.preventDefault() vs return false in JavaScript

When working with JavaScript event handling, you will often use the event.preventDefault and return false in JavaScript. Both are essential tools used to prevent default browser behaviors. Both of these can be used to prevent certain default behaviours, like stopping a form submission or preventing a link from navigating. event.preventDefault and return false in JavaScript are not the same and work differently depending on the context. In this article, we will discuss an event.preventDefault vs return false in JavaScript, and best practices regarding these methods.

Table of Contents:

• Understanding event.preventDefault in JavaScript
• return false in JavaScript
  • Example 1: Using Inline Event Handlers
  • Example 2: Same Example Using Event Listener
• Difference Between preventDefault and return false
• Using event.preventDefault & event.stopPropagation Together
• Best Practices for Using the event.preventDefault and return false in JavaScript
• Conclusion

Understanding event.preventDefault in JavaScript

The event.preventDefault in JavaScript is a method in JavaScript event handling that explicitly prevents the default behavior of an event without stopping event bubbling (event on a child element moves to its parent elements) and event capturing (opposite to event bubbling). It ensures that the default behaviour of the event, such as navigating to a new page when clicking a link, is stopped.

Syntax:

event.preventDefault();

Example:

Output:

Explanation: In this example, the event.preventDefault in JavaScript prevents the default browser action but doesn’t stop the event from propagating to the parent element. Thus, when you click on the submit button, only logs are printed (Form Submission Prevented). The form submission is blocked.

return false in JavaScript

The return false in JavaScript works differently in different places. The behaviour of the return false in JavaScript depends on where it is used in inline event handlers in or in event listeners.

• In inline event handlers (onclick=”return false;”): It prevents the default action and stops event propagation (event bubbling and capturing).
• In event listeners (addEventListener): It doesn’t prevent default behaviour or stop propagation. 

Syntax:

return false;

Example 1: Using Inline Event Handlers

Output:

Explanation: In this example, you’re using return false in JavaScript to stop the default behavior of the browser. Whenever you click on the link (Intellipaat Courses), the browser doesn’t navigate you to a new page because the default behaviour is prevented.

Example 2: Using Event Listener

Output:

Explanation: When you are using the return false in JavaScript inside the eventListener, then return false has no effect. It still navigates you to the Intellipaat website.

event.preventDefault() vs return false

Here are some important points that show the difference between preventDefault and return false methods in JavaScript:

Using event.preventDefault & event.stopPropagation Together

If you want to stop both, the default behaviour of your browser and the event propagation (event bubbling and capturing). Then, using the event.preventDefault() & event.stopPropagation() together is a great choice for you.

Syntax:

document.getElementById("myButton").addEventListener("click", function(event) {
    event.preventDefault();
    event.stopPropagation();
})

Explanation: The event.preventDefault is used to stop the default behaviour, and event.stopPropagation is used to stop the event bubbling and event capturing.

Best Practices for Using the event.preventDefault and return false in JavaScript

Here are some of the best practices that you have to take care of while using the event.preventDefault and return false in JavaScript:

• Always use event.preventDefault in JavaScript because it is a standard and efficient method to stop default actions of the browser in modern JavaScript.
• Avoid using return false in JavaScript inside event listeners.
• Use the event.stopPropagation() when you want to stop event bubbling, rather than depending on return false in JavaScript.
• Avoid inline event handlers (onclick=”return false;”).

Conclusion

Understanding the difference between event.preventDefault and return false is important for writing clean and efficient JavaScript code. If you are working with JavaScript event handling methods, then always use the event.preventDefault in JavaScript over return false. because it’s a clear and standard approach to stop the default actions of browsers. By using these best practices, you can ensure that your event handling logic works as you write code.

event.preventDefault() vs return false in JavaScript – FAQs