Null check for a value is not working in Javascript

Question

I am trying to null check in one input field and pop up a required message in another input field. To achieve this function i have used the below Javascript code.

$(document).on('change', '.address',function () {


  if ($(this).val() == null ) {
    $('#cutomer_id').prop('required',true);
  }
});

but this is not working as expected. but when i try the opposite if ($(this).val() != null ) its fire the required messege.

Because it's not actually null? Print it and see https://stackoverflow.com/questions/4456336/finding-variable-type-in-javascript. — jarmod, Jul 06 '21 at 19:08
console.log($(this).val()) is the absolute first thing you should do. — Tushar Shahi, Jul 06 '21 at 19:18

score 1 · Answer 1 · answered Jul 06 '21 at 21:21

It's because null is an object, but value of element is a string

What you need is check against an empty string:

if (this.value.trim() == "")
{
  $('#cutomer_id').prop('required',true);
}

The trim() added to remove trailing spaces.

P.S. please avoid unnecessary use of jquery or any other bloatware, $(this).val() is absolutely ridiculously unnecessary

Null check for a value is not working in Javascript

1 Answers1