CODEWITHSUNDEEP
javascriptjqueryobjectvariablesnull
Nida Amin
Nida Amin

Reputation: 755

Checking for null is not working for ajax json data

I am getting data from ajax call like

[{"_id":{"$oid":"5bd00e99d2ccda119c0032da"},"AllotmentsDetails":null}]

I am comparing it for null value like

var allotmentDetailsArray = data[0]['AllotmentsDetails'];

if (allotmentDetailsArray.length == 0 || allotmentDetailsArray == null)
{
    ////
}

It is not going in if condition... Please help !!!

Upvotes: 1

Views: 945

Answers (5)

MahalingaM SubramaniyaM
MahalingaM SubramaniyaM

Reputation: 99

First you have to check null or not null. if its not null means then check length.

Please try it.

//Ex:1
var data= [{"_id":{"$oid":"5bd00e99d2ccda119c0032da"},"AllotmentsDetails":null}];

var allotmentDetailsArray = data[0]['AllotmentsDetails'];

if (allotmentDetailsArray == null)
{
    alert(allotmentDetailsArray);
}
else if(allotmentDetailsArray.length == 0)
{
    alert(allotmentDetailsArray.length);
}
//or
if (allotmentDetailsArray == null ||allotmentDetailsArray.length == 0 )
{
alert(allotmentDetailsArray);
}

//Ex:2
var data= [{"_id":{"$oid":"5bd00e99d2ccda119c0032da"},"AllotmentsDetails":""}];

 allotmentDetailsArray = data[0]['AllotmentsDetails'];

if (allotmentDetailsArray == null)
{
    alert(allotmentDetailsArray);
}
else if(allotmentDetailsArray.length == 0)
{
    alert(allotmentDetailsArray.length);
}

Upvotes: 1

haMzox
haMzox

Reputation: 2109

You cannot check length of a null value. However you can check null value and array length with this code.

if (!allotmentDetailsArray) {
  // null check here. you cannot check array length here since it's a null value
} else {
  // if you want to check array length 
  if (allotmentDetailsArray.length === 0 ) {
    // check here
  }
}

Upvotes: 1

cнŝdk
cнŝdk

Reputation: 32145

You have to check against null before trying to access the object, in your if block you are trying to call .length on a null object.

You can do it like this:

if (!allotmentDetailsArray || allotmentDetailsArray.length == 0)
{
    ////
}

Where !allotmentDetailsArray is a shortened expression for allotmentDetailsArray == null which checks that allotmentDetailsArray is undefined or null.

So here the second part of the if block is only checked when allotmentDetailsArray is not null.

Upvotes: 3

Wise Randr
Wise Randr

Reputation: 25

You can just check the type:

var allotmentDetailsArray = data[0]['AllotmentsDetails'];

if (typeof allotmentDetailsArray !== "undefined")
{
  // Var is not null
}

Upvotes: 0

Rajasekhar
Rajasekhar

Reputation: 527

You have to check null first then check for length

if (allotmentDetailsArray == null || allotmentDetailsArray.length == 0)
{
      ////
}

Upvotes: 2

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