What Does `return false` Do in an HTML Event Listener?

The Impact of 'return false' in Event Listeners

In HTML, you might encounter links like this:

<a href='#' onclick='someFunc(3.1415926); return false;'>Click here !</a>

This code raises the question: what does the 'return false' addition achieve?

Effect of 'return false'

The return value of an event handler dictates whether the browser should proceed with its default action. In the case of links, the default action is to follow the link. By returning 'false', you prevent this default behavior.

Significance in Buttons

While you may not commonly see 'return false' in button event listeners, it serves the same purpose: canceling the button's default action, such as form submission.

Specifying 'return false'

There isn't a specific W3C spec for 'return false' in event handlers. Such ancient JavaScript interfaces fall under the umbrella of "DOM 0," which lacks formal documentation. Referencing old Netscape 2 documentation may provide some insights.

Modern Alternative

The modern approach to canceling default event behavior is to use event.preventDefault(), as specified in the DOM 2 Events spec. This clears up any ambiguity associated with 'return false' and ensures cross-browser compatibility.

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