Load Only a Section of a Page

Use Case

You want to AJAX load a section of another page on your site onto the current page. Say your eCommerce CMS system creates a dynamic menu of products, but that exists as a subdirectory of your site and you want to use that on the homepage.

#JQuery

$("#mainNav").load("/store #mainNav")

The first param is the URL (only works for same-domain requests!) and the 

second (well, technically it's still part of the first, separated by a space) is a jQuery selector

 of the part to load. Not passing the second selector param will load the entire page. 

There is an optional third parameter, a callback function, which will run when the load is 

complete.

Load jQuery Only If Not Present

Say you were going to do an include on a whole bunch of pages, and inside of that include you wanted to do some jQuery specific stuff. That page may or may not already have jQuery loaded. If it already does, you don't want to load it again, but if not, you do. This works for that.

Smart Asynchronous Way

// Only do anything if jQuery isn't defined
if (typeof jQuery == 'undefined') {

 if (typeof $ == 'function') {
  // warning, global var
  thisPageUsingOtherJSLibrary = true;
 }
 

jQuery Duplicate Plugin

$.fn.duplicate = function(count, cloneEvents) {
       var tmp = [];
       for ( var i = 0; i < count; i++ ) {
               $.merge( tmp, this.clone( cloneEvents ).get() );
       }
       return this.pushStack( tmp );
};

The .clone() function of jQuery will duplicate a set once, but what if you need multiple 
copies of the same set? You would have to do:

$(elem)
   .clone()
   .appendTo(otherElem)
   .clone()
   .appendTo(otherElem)
   .clone()
   .appendTo(otherElem);
Now you can just:

$(elem)
   .duplicate(n)
   .appendTo(otherElem);
The first parameter is the number of clones you want and the second optional parameter 
is a boolean which controls if you want the events bound to those existing elements to be attached to the clones as well (or not).

Force iframe to Reload

$('iframe').attr('src', $('iframe').attr('src'));

Fallback for CDN hosted jQuery

Several big companies offer copies of jQuery hosted on their CDN's (Content Delivery Network). Most notoriously Google, but also Microsoft and jQuery themselves. A lot of people swear by this since it saves bandwidth, downloads faster, and perhaps even stays cached jumping between different sites that use the same script.

There is always that twinge of doubt though, that perhaps something goes wrong with these big companies CDN at the script isn't available (it happens). It's more reliable to use your own website, as hey, if they are loading your webpage, then your server is up and will server the script just fine, albeit with out the benefits of the CDN.

So perhaps the best solution is to use both methods! Use the CDN first, and if it fails, load the local copy. Here is a technique:

<script type="text/javascript" src="http://ajax.microsoft.com/ajax/jquery/jquery-1.4.2.min.js"></script>
<script type="text/javascript">
if (typeof jQuery == 'undefined') {
    document.write(unescape("%3Cscript src='/js/jquery-1.4.2.min.js' type='text/javascript'%3E%3C/script%3E"));
}
</script>

Find all Internal Links

Find all links that start with the sites domain, a slash, relative file path, or a hashtag.

var siteURL = "http://" + top.location.host.toString();

var $internalLinks = $("a[href^='"+siteURL+"'], a[href^='/'], a[href^='./'], a[href^='../'], a[href^='#']");

Draggable without jQuery UI

It doesn't have all the fancy callbacks and options, but hey, it makes things draggable (and with a specified handle optionally).

(function($) {
    $.fn.drags = function(opt) {

        opt = $.extend({handle:"",cursor:"move"}, opt);

        if(opt.handle === "") {
            var $el = this;
        } else {
            var $el = this.find(opt.handle);
        }

        return $el.css('cursor', opt.cursor).on("mousedown", function(e) {
            if(opt.handle === "") {
                var $drag = $(this).addClass('draggable');
            } else {
                var $drag = $(this).addClass('active-handle').parent().addClass('draggable');
            }
            var z_idx = $drag.css('z-index'),
                drg_h = $drag.outerHeight(),
                drg_w = $drag.outerWidth(),
                pos_y = $drag.offset().top + drg_h - e.pageY,
                pos_x = $drag.offset().left + drg_w - e.pageX;
            $drag.css('z-index', 1000).parents().on("mousemove", function(e) {
                $('.draggable').offset({
                    top:e.pageY + pos_y - drg_h,
                    left:e.pageX + pos_x - drg_w
                }).on("mouseup", function() {
                    $(this).removeClass('draggable').css('z-index', z_idx);
                });
            });
            e.preventDefault(); // disable selection
        }).on("mouseup", function() {
            if(opt.handle === "") {
                $(this).removeClass('draggable');
            } else {
                $(this).removeClass('active-handle').parent().removeClass('draggable');
            }
        });

    }
})(jQuery);

Usage

$('div').drags();

Display Browser and Version

This is jQuery specific, and contains a bit of a hack/fix for dealing with Chrome. This works between jQuery 1.5.1 and jQuery 1.8.3. It's gone in jQuery 1.9. Presumably because it was used too improperly too frequently and it was hurting the web. Better to feature detect when possible.

var userAgent = navigator.userAgent.toLowerCase(),
    browser   = '',
    version   = 0;

$.browser.chrome = /chrome/.test(navigator.userAgent.toLowerCase());

// Is this a version of IE?
if ($.browser.msie) {
  userAgent = $.browser.version;
  userAgent = userAgent.substring(0,userAgent.indexOf('.')); 
  version = userAgent;
  browser = "Internet Explorer";
}

// Is this a version of Chrome?
if ($.browser.chrome) {
  userAgent = userAgent.substring(userAgent.indexOf('chrome/') + 7);
  userAgent = userAgent.substring(0,userAgent.indexOf('.')); 
  version = userAgent;
  // If it is chrome then jQuery thinks it's safari so we have to tell it it isn't
  $.browser.safari = false;
  browser = "Chrome";
}

// Is this a version of Safari?
if ($.browser.safari) {
  userAgent = userAgent.substring(userAgent.indexOf('safari/') + 7); 
  userAgent = userAgent.substring(0,userAgent.indexOf('.'));
  version = userAgent; 
  browser = "Safari";
}

// Is this a version of Mozilla?
if ($.browser.mozilla) {
 //Is it Firefox?
 if (navigator.userAgent.toLowerCase().indexOf('firefox') != -1) {
  userAgent = userAgent.substring(userAgent.indexOf('firefox/') + 8);
  userAgent = userAgent.substring(0,userAgent.indexOf('.'));
  version = userAgent;
  browser = "Firefox"
 }
 // If not then it must be another Mozilla
 else {
   browser = "Mozilla (not Firefox)"
 }
}

// Is this a version of Opera?
if ($.browser.opera) {
 userAgent = userAgent.substring(userAgent.indexOf('version/') + 8);
 userAgent = userAgent.substring(0,userAgent.indexOf('.'));
 version = userAgent;
 browser = "Opera";
}

// Now you have two variables, browser and version
// which have the right info

Check if Event was Triggered or Native

$('button').click(function(event, wasTriggered) {
    if (wasTriggered) {
        alert('triggered in code');
    } else {
        alert('triggered by mouse');
    }
});

$('button').trigger('click', true);

Check if jQuery is Loaded

if (typeof jQuery == 'undefined') {

    // jQuery IS NOT loaded, do stuff here.

}