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Chris Ferdinandi

Hi, Iā€™m Chris Ferdinandi. I help people learn vanilla JavaScript through my guides, courses, and daily developer tips. I love pirates, puppies, and Pixar movies.

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Form Validation – Part 4: Validating the MailChimp Subscribe Form

Over the last few articles in this series, we've learned how to use a handful of input types and validation attributes to natively validate forms.

We've learned how to use the Constraint Validation API to enhance the native browser validation process for a better overall user experience. And we wrote a polyfill to extend support all the way back to IE9 (and plug a few feature holes in some newer versions).

Now, let's take what we've learned and apply it … Read article

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Form Validation Part 3: A Validity State API Polyfill

In the last article in this series, we built a lightweight script (6kb, 2.7kb minified) using the Validity State API to enhance the native form validation experience. It works in all modern browsers and provides support IE support back to IE10. But, there are some browser gotchas.

Not every browser supports every Validity State property. Internet Explorer is the main violator, though Edge does lack support for tooLong even though IE10+ support it. And Chrome, Firefox, and Safari got … Read article

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Form Validation Part 2: The Constraint Validation API (JavaScript)

In my last article, I showed you how to use native browser form validation through a combination of semantic input types (for example, <input type="email"/>) and validation attributes (such as required and pattern).

While incredibly easy and super lightweight, this approach does have a few shortcomings.

  1. You can style fields that have errors on them with the :invalid pseudo-selector, but you can't style the error messages themselves.
  2. Behavior is also inconsistent across browsers.

User studies from Christian HolstRead article

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Form Validation Part 1: Constraint Validation in HTML

Most JavaScript form validation libraries are large, and often require other libraries like jQuery. For example, MailChimp's embeddable form includes a 140kb validation file (minified). It includes the entire jQuery library, a third-party form validation plugin, and some custom MailChimp code. In fact, that setup is what inspired this new series about modern form validation. What new tools do we have these days for form validation? What is possible? What is still needed?

In this series, I'm going to show … Read article

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