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

Question

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?

what kind of element is #person_data? and what do you consider as a NULL value? — , Nov 22 '10 at 10:45

score 194 · Accepted Answer · answered Nov 22 '10 at 10:47

194

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 ) {...}
}

answered Nov 22 '10 at 10:47

Guffa

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`The value of a field can not be null, it's always a string value.` this isn't entirely true. I've got a `select` containing no `options`. When I perform `.val()` on this it returns `null`. Jquery 1.7.2 – Liam Jan 14 '13 at 11:07
@Pispirulito: I don't think so, and I don't think that it will be changed. A `select` without any `option` elements is not something that you normally have. It's pretty useless. – Guffa Jan 30 '14 at 21:22
1

@Guffa beg to differ, an empty ` – Malcolm Salvador Aug 01 '17 at 03:18
If you use the following solution to provide a placeholder in your `select`, it will start out with a `null` value because a 'disabled' option is selected. https://stackoverflow.com/questions/5805059/how-do-i-make-a-placeholder-for-a-select-box – Sygmoral May 04 '19 at 01:51
This worked for me not equal null `if ($('#person_data[document_type]').val() !== null){}` – SWAT 10101 Nov 26 '21 at 17:40

Flipke · Answer 2 · 2010-11-22T13:06:20.857

38

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

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

}

edited Nov 22 '10 at 13:06

answered Nov 22 '10 at 10:49

Flipke

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score 17 · Answer 3 · answered Nov 22 '10 at 10:50

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.

score 15 · Answer 4 · edited Jan 16 '17 at 12:29

15

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'

edited Jan 16 '17 at 12:29

Wirone

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answered May 20 '15 at 19:52

Allan Felipe Murara

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score 8 · Answer 5 · answered Jan 28 '16 at 08:07

_helpers: {
        //Check is string null or empty
        isStringNullOrEmpty: function (val) {
            switch (val) {
                case "":
                case 0:
                case "0":
                case null:
                case false:
                case undefined:
                case typeof this === 'undefined':
                    return true;
                default: return false;
            }
        },

        //Check is string null or whitespace
        isStringNullOrWhiteSpace: function (val) {
            return this.isStringNullOrEmpty(val) || val.replace(/\s/g, "") === '';
        },

        //If string is null or empty then return Null or else original value
        nullIfStringNullOrEmpty: function (val) {
            if (this.isStringNullOrEmpty(val)) {
                return null;
            }
            return val;
        }
    },

Utilize this helpers to achieve that.

this almost seems like `isStringNullOrEmpty` is `isStringFalsey` and thus `return !val;` would work — Mark Schultheiss, Oct 28 '19 at 15:11

score 0 · Answer 6 · answered Nov 22 '10 at 10:48

0

jquery provides val() function and not value(). You can check empty string using jquery

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

answered Nov 22 '10 at 10:48

Chinmayee G

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score 0 · Answer 7 · answered Apr 23 '19 at 09:23

0

Try

if( this["person_data[document_type]"].value != '') { 
  console.log('not empty');
}

<input id="person_data[document_type]" value="test" />

answered Apr 23 '19 at 09:23

Kamil Kiełczewski

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score 0 · Answer 8 · answered Jan 08 '21 at 10:51

0

My Working solution is

var town_code = $('#town_code').val(); 
 if(town_code.trim().length == 0){
    var town_code = 0;
 }

answered Jan 08 '21 at 10:51

Anes

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MB_18 · Answer 9 · 2022-05-09T10:57:08.853

0

In your code 'NULL' is a string. So its wrong.

You can use exclamation mark ! to check if it is null.

Here is the code:

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

}

The above code means that if the $('#person_data[document_type]') has no value (if the value is null).

edited May 09 '22 at 10:57

answered May 09 '22 at 08:33

MB_18

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

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