if(isiOS){
       // implement double-tap
}else{
       // implement double click
}

$(selector).bind('touchend', function(event){
       var now = new Date().getTime();
       var lastTouch = $(this).data('lastTouch') || now + 1 /** the first time this will make delta a negative number */;
       var delta = now - lastTouch;
       if(delta<500 && delta>0){
               // the second touchend event happened within half a second. Here is where we invoke the double tap code
       }else{
               // A click/touch action could be invoked here but wee need to wait half a second before doing so.
       }
       $(this).data('lastTouch', now);
}

var action;
$(selector).bind('touchend', function(event){
       var now = new Date().getTime();
       var lastTouch = $(this).data('lastTouch') || now + 1 /** the first time this will make delta a negative number */;
       var delta = now - lastTouch;
       clearTimeout(action);
       if(delta<500 && delta>0){
               // the second touchend event happened within half a second. Here is where we invoke the double tap code
       }else{
               $(this).data('lastTouch', now);
               action = setTimeout(function(e){
                       // If this runs you can invoke your 'click/touchend' code
                       clearTimeout(action);   // clear the timeout
               }, 500, [event]);
       }
       $(this).data('lastTouch', now);
}

/*!
 * jQuery Double Tap Plugin.
 *
 * Copyright (c) 2010 Raul Sanchez (http://www.appcropolis.com)
 *
 * Dual licensed under the MIT and GPL licenses:
 * http://www.opensource.org/licenses/mit-license.php
 * http://www.gnu.org/licenses/gpl.html
 */
 
(function($){
    // Determine if we on iPhone or iPad
    var isiOS = false;
    var agent = navigator.userAgent.toLowerCase();
    if(agent.indexOf('iphone') >= 0 || agent.indexOf('ipad') >= 0){
           isiOS = true;
    }
 
    $.fn.doubletap = function(onDoubleTapCallback, onTapCallback, delay){
        var eventName, action;
        delay = delay == null? 500 : delay;
        eventName = isiOS == true? 'touchend' : 'click';
 
        $(this).bind(eventName, function(event){
            var now = new Date().getTime();
            var lastTouch = $(this).data('lastTouch') || now + 1 /** the first time this will make delta a negative number */;
            var delta = now - lastTouch;
            clearTimeout(action);
            if(delta<500 && delta>0){
                if(onDoubleTapCallback != null && typeof onDoubleTapCallback == 'function'){
                    onDoubleTapCallback(event);
                }
            }else{
                $(this).data('lastTouch', now);
                action = setTimeout(function(evt){
                    if(onTapCallback != null && typeof onTapCallback == 'function'){
                        onTapCallback(evt);
                    }
                    clearTimeout(action);   // clear the timeout
                }, delay, [event]);
            }
            $(this).data('lastTouch', now);
        });
    };
})(jQuery);

$(selector).doubletap(
    /** doubletap-dblclick callback */
    function(event){
        alert('double-tap');
    },
    /** touch-click callback (touch) */
    function(event){
        alert('single-tap');
    },
    /** doubletap-dblclick delay (default is 500 ms) */
    400
);