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How do I get number of fields in JavaScript object?

rated 0 times [ 127] [ 6] / answers: 1 / hits: 26445 / 15 Years ago, thu, july 2, 2009, 12:00:00

I'm trying to use JavaScript object as an associative array and everything was well until I needed to get number of entries that are stored in it. What is the easiest and most elegant way to do that? All I can think of is to run for each loop or jQuery $.each function and just see how much iterations it would do but that looks like an an awful thing to do.

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grayson

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answered 15 Years ago kennedi · Accepted Answer

Old Firefox supports the __count__ property. Newer environments support ES5's Object.keys. For older environments we have to fallback to just iterating over the object and counting manually (ugh!):

function count(obj) {



    if (obj.__count__ !== undefined) { // Old FF

        return obj.__count__;

    }



    if (Object.keys) { // ES5 

        return Object.keys(obj).length;

    }



    // Everything else:



    var c = 0, p;

    for (p in obj) {

        if (obj.hasOwnProperty(p)) {

            c += 1;

        }

    }



    return c;



}