Cacher is the code snippet organizer for pro developers

(function($){

var hasTouch = /android|iphone|ipad/i.test(navigator.userAgent.toLowerCase()),
    eventName = hasTouch ? 'touchend' : 'click';

/**
 * Bind an event handler to the "double tap" JavaScript event.
 * @param {function} doubleTapHandler
 * @param {number} [delay=300]
 */
$.fn.doubletap = function(doubleTapHandler, delay){
    delay = (delay == null) ? 300 : delay;

    this.bind(eventName, function(event){
        var now = new Date().getTime();

        // the first time this will make delta a negative number
        var lastTouch = $(this).data('lastTouch') || now + 1;
        var delta = now - lastTouch;
        if(delta < delay && 0 < delta){
            // After we detct a doubletap, start over
            $(this).data('lastTouch', null);

            if(doubleTapHandler !== null && typeof doubleTapHandler === 'function'){
                doubleTapHandler(event);
            }
        }else{
            $(this).data('lastTouch', now);
        }
    });
};

})(jQuery);