CSS Day 2017

Peter-Paul Koch

Constraint Validation

Jun 2017

Form validation is literally the oldest trick in the JavaScript book: it was just about the only thing you could use JavaScript for in Netscape 2. Nowadays the state of the art has advanced with the Constraint Validation API and the CSS :invalid pseudo-class. That sounds great … until you actually try to use them.

In this presentation, PPK will discuss how the API works, why it is not all that great, and draw some valuable lessons about how not to design APIs. He’ll also tell you how to validate your forms properly.


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