Debounce keyup in JavaScript

valueChanged.js

(function ($, ku)
{
    var debounce = function (func)
    {
        var timeout;
        var lastValue;
        return function debounced()
        {
            var obj = this, args = arguments;
            function delayed()
            {
                if (obj.value !== lastValue) {
                    func.apply(obj, args);
                    lastValue = obj.value;
                }
                timeout = null;
            };

            if (timeout)
                clearTimeout(timeout);

            timeout = setTimeout(delayed, 500);
        };
    };
    jQuery.fn[ku] = function (fn) { return fn ? this.bind('keyup', debounce(fn)) : this.trigger(ku); };
})(jQuery, 'valueChanged');