How to check if some field does not exist in JavaScript

Question

I have jQuery code like

      for(var j in indivudvalbookdetails) {
         if(indivudvalbookdetails[j]['status'] == "") {
          ... 
         }
     }

Now there might be some items in the loop where status field won't exists, if there are such items the code in the if condition should work.

Instead of the empty character, check for undefined, and use strict comparison operator. — Teemu
– Teemu, Commented Nov 5, 2017 at 10:04

Narendra Lakhtariya · Accepted Answer · 2017-11-05 10:15:04Z

3

Try this:

var myElement =  indivudvalbookdetails[j]['status'];
if (typeof(myElement) != 'undefined' && myElement != null)
{
  // exists.
}

You can also try with JQuery like:

if ($('#elementId').length > 0) {
  // exists.
}

answered Nov 5, 2017 at 10:15

Narendra Lakhtariya

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Comments

Rafdro · Accepted Answer · 2017-11-05 11:35:00Z

3

Just check if its undefined:

if(typeof indivudvalbookdetails[j]['status'] === "undefined") { ...

edited Nov 5, 2017 at 11:35

answered Nov 5, 2017 at 10:13

Rafdro

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Comments

Onoulade · Accepted Answer · 2017-11-05 10:09:03Z

1

Your code is comparing your variable to an empty string. But if this variable is not defined, it can’t compare it, so you can do :

if(indivudvalbookdetails[j]['status'] == undefined)

If the « status » var is defined but just empty you can do

 if(indivudvalbookdetails[j]['status'] == null)

answered Nov 5, 2017 at 10:09

Onoulade

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2 Comments

Teemu Over a year ago

Non-existing/assigned values are returned as undefined. Strict comparison is needed, if the data contains zeros or empty characters.

Jonas Wilms Over a year ago

tldr: in most cases use ===. This is one.

vibhor1997a · Accepted Answer · 2017-11-05 10:12:16Z

1

You check like this

if(!indivudvalbookdetails[j]['status'])

answered Nov 5, 2017 at 10:12

vibhor1997a

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2 Comments

Jonas Wilms Over a year ago

Note that {status:""} wont pass the test

vibhor1997a Over a year ago

Sorry, didn't think of that. We would have to check for undefined and null as well

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