How do I test for an empty Javascript object from JSON?

Question

After an AJAX request, sometimes my application may return an empty object, like:

var a = ({});

How can I check if that's the case?

Answer 1

There's no easy way to do this. You'll have to loop over the properties explicitly:

function isEmpty(obj) {
    for(var prop in obj) {
        if(obj.hasOwnProperty(prop))
            return false;
    }

    return true;
}

Answer 2

1) Just a workaround. Can your server generate some special property in case of no data? For example:

var a = {empty:true};

Then you can easily check it in your AJAX callback code.

2) Another way to check it:

if (a.toSource() === "({})")  // then `a` is empty

EDIT: If you use any JSON library (f.e. JSON.js) then you may try JSON.encode() function and test the result against empty value string.

Answer 3

function isEmpty(obj) { for(var i in obj) { return false; } return true; }

Answer 4

In addition to Thevs answer:

var o = {};
alert($.toJSON(o)=='{}'); // true

var o = {a:1};
alert($.toJSON(o)=='{}'); // false

it's jquery + jquery.json

Answer 5

you must be binding this json to some dom element inspite of checking json best way is to make the the binding function handle such data

Answer 6

For those of you who have the same problem but uses jQuery, you can use jQuery.isEmptyObject.

Answer 7

How about:

if (a.length != undefined) {
    // a is good, go ahead
}

This works for me.

Answer 8

Here is another way:

a ={};

var b= {

        x: function() { return 'x' }
}

function isNotEmpty(obj) {
return (obj.__count__);
}

alert(isNotEmpty(a));

alert(isNotEmpty(b));

The aim of this function is to detect properties directly on obj.Zero(0) indicates no properties

Answer 9

it's very simple

if is json, i always contains '{}'

so you should write :

"data" is string Json as : {'name':'phucvh', 'age':'21'}

if (data.charAt(0) == '{')

{

alert('is Json');

}