html5 oninvalid doesn't work after fixed the input field

Question

I have this input code in my form:

Answer 1

If you setCustomValidity to any value that is not the empty string then that will cause the input to be in the invalid state. So your condition is checking for a value, then setting the field to be invalid either way. Only setCustomValidity when the value in the field is actually invalid, otherwise set it to an empty string: