//http://unscriptable.com/index.php/2009/03/20/debouncing-javascript-methods/
Function.prototype.debounce = function (threshold, execAsap) {
    var func = this, // reference to original function
        timeout; // handle to setTimeout async task (detection period)
    // return the new debounced function which executes the original function only once
    // until the detection period expires
    return function debounced () {
        var obj = this, // reference to original context object
            args = arguments; // arguments at execution time
        // this is the detection function. it will be executed if/when the threshold expires
        function delayed () {
            // if we're executing at the end of the detection period
            if (!execAsap)
                func.apply(obj, args); // execute now
            // clear timeout handle
            timeout = null; 
        };
        // stop any current detection period
        if (timeout)
            clearTimeout(timeout);
        // otherwise, if we're not already waiting and we're executing at the beginning of the detection period
        else if (execAsap)
            func.apply(obj, args); // execute now
        // reset the detection period
        timeout = setTimeout(delayed, threshold || 100); 
    };
};