:valid, :invalid, and :required CSS Pseudo Classes

By  on  

Let's be honest, form validation with JavaScript can be a real bitch.  On a real basic level, however, it's not that bad.  HTML5 has jumped in to some extent, providing a few attributes to allow us to mark fields as required or only valid if matching a given regular expression.  What some people don't know is that you can style elements base on their required, valid, or invalid values.  Here's how!

The CSS

Each state is colon-separated from the element it's associated with:

/* basics */
input:required {
	border: 1px solid blue;
}
input:valid {
	border: 1px solid green;
}
input:invalid {
	border: 1px solid red;
}

These pseudo classes are straight forward and useful. Here we're changing only borders, but you could use :before and :after to place text or an image next to each field, representing their state.

Being able to style elements based on invalid or valid information is something we've shimmed forever with JavaScript, but now we can do so (to some degree) with pure CSS!

Recent Features

  • By
    Responsive and Infinitely Scalable JS Animations

    Back in late 2012 it was not easy to find open source projects using requestAnimationFrame() - this is the hook that allows Javascript code to synchronize with a web browser's native paint loop. Animations using this method can run at 60 fps and deliver fantastic...

  • By
    5 HTML5 APIs You Didn’t Know Existed

    When you say or read "HTML5", you half expect exotic dancers and unicorns to walk into the room to the tune of "I'm Sexy and I Know It."  Can you blame us though?  We watched the fundamental APIs stagnate for so long that a basic feature...

Incredible Demos

  • By
    Create a Dynamic Flickr Image Search with the Dojo Toolkit

    The Dojo Toolkit is a treasure chest of great JavaScript classes.  You can find basic JavaScript functionality classes for AJAX, node manipulation, animations, and the like within Dojo.  You can find elegant, functional UI widgets like DropDown Menus, tabbed interfaces, and form element replacements within...

  • By
    Fullscreen API

    As we move toward more true web applications, our JavaScript APIs are doing their best to keep up.  One very simple but useful new JavaScript API is the Fullscreen API.  The Fullscreen API provides a programmatic way to request fullscreen display from the user, and exit...

Discussion

  1. A small note: :before and :after only works with elements that have content. inputs doesn’t, so these pseudo-elements won’t work.

  2. Amazing post, so in your example you are testing it with input text and email address is that all ?!

  3. “now we can do so (to some degree) with pure CSS!”

    could you please go into more detail about that degree? Browser support? Is this CSS3 only?

  4. @Sumit – I can’t find any references on caniuse.com or anything similar. From my testing it works on: latest Chrome, latest Firefox, lateset Safari and IE10+. It doesn’t work on IE9 or below.

  5. The :before and :after pseudo-elements elements interact with other boxes… as if they were real elements inserted just inside their associated element. More… http://www.corelangs.com/css/basics/pseudo.html CSS pseudo-elements

    Eric

  6. Diego Leme

    Bug in IE usign pseudo-elements
    http://codepen.io/diegoleme/pen/cJyjF

  7. A pseudo-class is similar to a class in HTML, but it’s not specified explicitly in the markup. Some pseudo-classes are dynamic — they’re applied as a result of user interaction with the document.
    for full implementation of pseudo class to refer here:
    http://www.mindstick.com/blog/711/CSS%20Pseudo%20Class

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