Is it important to verify data as well as HTML5 checks?

Here’s an example from the Programming Elm book. It disables the form button for an empty string. It seems to work fine without the duplicate check for empty strings (it won’t post when pressing the button, or pressing Enter).

I’m wondering the same thing for the likes of:

If you were communicating to a server, I think conventional wisdom says to validate at server-side too. So perhaps this is important if you’re validating json to post.[1]


  1. You might also want to see “What is the “Elm Way” to validate form fields?”. ↩︎

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