Testing for an empty array object in JSON with jQuery

Question

I have a request that returns a JSON object with a single property which is an array. How can I test if the array is empty?

With jQuery code like:

 $.getJSON(
            jsonUrl,
            function(data) {
                if (data.RoleOwners == [ ]) {
                    $('<tr><td>' + noRoleOwnersText + '</td></tr>').appendTo("#roleOwnersTable tbody");
                    return;
                }
                $.each(data.RoleOwners, function(i, roleOwner) {
                    var tblRow =
                    "<tr>"
                    + "<td>" + roleOwner.FirstName + "</td>"
                    + "<td>" + roleOwner.LastName + "</td>"
                    + "</tr>"
                    $(tblRow).appendTo("#roleOwnersTable tbody");
                });

what can I put instead of if(data.RoleOwners == [ ]) to test if the RoleOwners is an empty array?

Thanks, Matt

Svante Svenson · Accepted Answer · 2010-07-12 16:05:39Z

26

(data.RoleOwners.length === 0)

edited Jul 12, 2010 at 16:05

answered Dec 2, 2008 at 17:59

Svante Svenson

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4 Comments

Ed Gomoliako Over a year ago

I don't understand. Why -1? „![].length“ — would be shorter and correctly, imho.

balupton Over a year ago

Agreed, should be .length === 0, or ![].length as said above. Either way this question is not about JSON objects at all, but Javascript arrays.

mattcole Over a year ago

Lol thanks for that, thought I'd tried that, but I must have tried .Length instead.

Pedro Montoto García Over a year ago

Cyle stackoverflow.com/questions/5447024/…

Sadiksha Gautam · Accepted Answer · 2011-08-02 11:31:47Z

23

You can also do jQuery.isEmptyObject(data.RoleOwners)

check out http://api.jquery.com/jQuery.isEmptyObject/

answered Aug 2, 2011 at 11:31

Sadiksha Gautam

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1 Comment

JakeJ Over a year ago

This answer worked when an empty array or a null array is passed through the data result (The accepted answer didn't) thanks for this

Arun Pratap Singh · Accepted Answer · 2013-09-18 12:17:14Z

4

below code works perfectly fine no need to write one of yours own.

   // anyObjectIncludingJSON i tried for JSON object.

         if(jQuery.isEmptyObject(anyObjectIncludingJSON))
            {
                return;
            }

answered Sep 18, 2013 at 12:17

Arun Pratap Singh

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1 Comment

Archana Mundaye Over a year ago

Arun, I observed that you have good understanding on jQuery apis, you have always given reference of Jquery's inbuilt apis rather than re-inventing ..wheels..good

Sameera Prasad Jayasinghe · Accepted Answer · 2018-03-23 07:03:46Z

1

Check this

JSON.parse(data).length > 0

answered Mar 23, 2018 at 7:03

Sameera Prasad Jayasinghe

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Comments

John Middlemas · Accepted Answer · 2012-05-15 03:54:25Z

0

An array (being an object too) can have non numeric properties which are not picked up by testing for zero length. You need to iterate through the properties just like testing for an empty object. If there are no properites then the array is empty.

function isEmptyObject(obj) {
   // This works for arrays too.
   for(var name in obj) {
       return false
   }
   return true
}

answered May 15, 2012 at 3:54

John Middlemas

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