Calulating length in Javascript

This question already has an answer here:

Length of a JavaScript object 32 answers

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You can do this:

Object.getOwnPropertyNames(treeObj).length;  // 3

getOwnPropertyNames returns array of properties of treeObj whose length can be checked.

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To count the number of properties an object has, you need to loop through the properties but remember to use the hasOwnProperty function:

var count = 0;
for (var p in obj) {
    if (obj.hasOwnProperty(p)) {
        count++;
    }
}

If you forget to do that, you will be looping through inherited properties. If you (or some library) has assigned a function to the prototype of Object, then all objects will seem to have that property, and thus will seem one item "longer" than they intrinsically are.

consider using jQuery's each instead:

var count = 0;
$.each(obj, function(k, v) { count++; });

OR simply,

 for (var p in obj) 
            count++;

UPDATE With current browsers:

Object.keys(someObj).length

Refer Old Post

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