jQuery: checking if the value of a field is null (empty)

Is this a good way to check if the value of a field is null?

if($('#person_data[document_type]').value() != 'NULL'){}

Or is there a better way?

Solution 1:

The value of a field can not be null, it's always a string value.

The code will check if the string value is the string "NULL". You want to check if it's an empty string instead:

if ($('#person_data[document_type]').val() != ''){}

or:

if ($('#person_data[document_type]').val().length != 0){}

If you want to check if the element exist at all, you should do that before calling val:

var $d = $('#person_data[document_type]');
if ($d.length != 0) {
  if ($d.val().length != 0 ) {...}
}

Solution 2:

I would also trim the input field, cause a space could make it look like filled

if ($.trim($('#person_data[document_type]').val()) != '')
{

}

Solution 3:

Assuming

var val = $('#person_data[document_type]').value();

you have these cases:

val === 'NULL';  // actual value is a string with content "NULL"
val === '';      // actual value is an empty string
val === null;    // actual value is null (absence of any value)

So, use what you need.

Solution 4:

that depends on what kind of information are you passing to the conditional..

sometimes your result will be null or undefined or '' or 0, for my simple validation i use this if.

( $('#id').val() == '0' || $('#id').val() == '' || $('#id').val() == 'undefined' || $('#id').val() == null )

NOTE: null != 'null'