Submit form only if username not already exist Javascript

Question

i have form code i know how to check username already exist or not by comparing with array. But the problem is that my form get submit in both case if my username is valid or not.
so how do i make my field not valid and my form do not get submited when i enter the username that already exist in data storage.

Check my javascript file in the given code
https://code.sololearn.com/WFrHDCpul4SB/?ref=app

Answer 1

Use setCustomValidity method of the input element

https://code.sololearn.com/WJnWZZZlj8C1/?ref=app

https://developer.mozilla.org/en-US/docs/Web/API/HTMLObjectElement/setCustomValidity

Answer 2

Calviղ thanks

Answer 3

george
Morpheus
Ipang
Calviղ