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December 18, 2009

Object Type in Javascript

Someone noted the interesting line that I use to find the object type.

function getType(obj){
    if (obj === undefined) { return 'undefined'; }
    if (obj === null) { return 'null'; }
    return Object.prototype.toString.call(obj).split(' ').pop().split(']').shift().toLowerCase();
}

Object.prototype.getType = function(){
    return Object.prototype.toString.call(this).split(' ').pop().split(']').shift().toLowerCase();
};

I posted the QUnit test suite. I’ve tested it in IE6-8, Safari 4, and Firefox 3.5.6. It would be greatly appreciated if you post your results.

While the typical method of using typeof or instanceof may produce results, they have their faults.

Douglas Crockford writes about type detection and his methods work for most cases, but not all.

On a side note, the reason why the Object.prototype.getType doesn’t check for undefined or null is because neither of those have properties, that is, they are not an Object. That said, they cannot call any functions.