JavaScript Event.defaultPrevented

By  on  

Whether you started with the old on_____ property or addEventListener, you know that events drive user experiences in modern JavaScript. If you've worked with events, you know that preventDefault() and stopPropagation() are frequently used to handle events. One thing you probably didn't know: there's a defaultPrevented proptery on events!

Consider the following block of code:

// Specific to a link
const link = document.querySelector('#my-link');
link.addEventListener('click', e => e.preventDefault());

// A larger document scope
document.addEventListener('click', documentClickHandler);
function documentClickHandler(event) {
    if (event.defaultPrevented) {// Using the property
        // Do one thing if the click has been handled
    }
    else {
        // Otherwise do something fresh
    }
}

When preventDefault is called on a given event, the defaultPrevented property gets toggled to true. Due to event propagation, the event bubbles upward with this defaultPrevented value.

I've been handling events for two decades and didn't know this property existed until now. What's great about defaultPrevented is that it stays with the event without needing to track track it globally!

Recent Features

  • By
    CSS @supports

    Feature detection via JavaScript is a client side best practice and for all the right reasons, but unfortunately that same functionality hasn't been available within CSS.  What we end up doing is repeating the same properties multiple times with each browser prefix.  Yuck.  Another thing we...

  • By
    Tips for Starting with Bitcoin and Cryptocurrencies

    One of the most rewarding experiences of my life, both financially and logically, has been buying and managing cryptocurrencies like Bitcoin, Litecoin, Ethereum. Like learning any other new tech, I made rookie mistakes along the way, but learned some best practices along the way. Check out...

Incredible Demos

Discussion

    Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!