Javascript null or empty string does not work

Question

I am trying to test that my string is null or empty, however it does not work.

My Code :

var veri = {
  YeniMusteriEkleTextBox: $('#MyTextbox').val(),
};

if (veri.YeniMusteriEkleTextBox === "" || 
    veri.YeniMusteriEkleTextBox == '' || 
    veri.YeniMusteriEkleTextBox.length == 0 || 
    veri.YeniMusteriEkleTextBox == null) {
  alert("Customer Name can not be empty!!!");
}

How can ı check YeniMusteriEkleTextBox is null or empty ?

Where is this code located? Inside of a document ready handler? — contradictioned
– contradictioned, Commented Sep 12, 2013 at 13:03
Notice that '' === "" and that checking for .length == 0 was equivalent when you did knew that it was a string — Bergi
– Bergi, Commented Sep 12, 2013 at 13:06

BenM · Accepted Answer · 2013-09-12 13:02:39Z

4

I would use the ! operator to test if it is empty, undefined etc.

if (!veri.YeniMusteriEkleTextBox) {
    alert("Customer Name can not be empty!!!");
}

Also you do not need the comma after YeniMusteriEkleTextBox: $('#MyTextbox').val(),

Also testing for a length on an object that may be undefined will throw an error as the length will not be 0, it will instead be undefined.

answered Sep 12, 2013 at 13:02

BenM

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Comments

Alnitak · Accepted Answer · 2013-09-13 06:45:46Z

2

You need to .trim the value to remove leading and trailing white space:

var veri = {
    YeniMusteriEkleTextBox: $('#YeniMusteriAdiTextbox_I').val().trim()
};

The .trim method doesn't exist on some older browsers, there's a shim to add it at the above MDN link.

You can then just test !veri.YeniMusteriEkleTextBox or alternatively veri.YeniMusteriEkleTextBox.length === 0:

if (!veri.YeniMusteriEkleTextBox) {
    alert("Customer Name can not be empty!!!");
}

answered Sep 13, 2013 at 6:45

Alnitak

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Comments

Community · Accepted Answer · 2017-05-23 12:06:20Z

1

You should use

if (!veri.YeniMusteriEkleTextBox) {

This also checks for undefined which is not the same as null

edited May 23, 2017 at 12:06

CommunityBot

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answered Sep 12, 2013 at 13:05

micha

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1 Comment

Jaime Torres Over a year ago

Additionally OP, if YeniMusteriEkleTextBox was null, your code would have a runtime exception as null does not have the property length. When using null/undefined checks, make sure those occur first as they are (1) the fastest and (2) minimize risk of runtime exceptions as we see here.

mplungjan · Accepted Answer · 2013-09-13 06:54:22Z

-1

Since no one else is suggestion $.trim, I will

Note I removed the trailing comma too and use the ! not operator which will work for undefined, empty null and also 0, which is not a valid customer name anyway

var veri = {
  YeniMusteriEkleTextBox: $.trim($('#MyTextbox').val())
};

if (!veri.YeniMusteriEkleTextBox) {
  alert("Customer Name can not be empty!!!");
}

answered Sep 13, 2013 at 6:54

mplungjan

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