jQuery.noConflict – Resolving conflicts with other javascript libraries that use $() function

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One of the reasons that make a software popular is its extensions and plugins. jQuery has plenty of plugins that do almost anything you want, from simple button hide to full blown galleries. Plugins let non developers easily add functionality they need to their websites and there are times when one might include more than one javascript library such as prototype.js, YUI or mootools with jQuery. They all use $ as their main function name. Including second library might brake the behavior of the first one. To resolve such cases jQuery introduces .noConflict() method.

When you call .noConflict() jQuery will return $() to it’s previous owner and you will need to use jQuery() instead of shorthand $() function.

.noConflict() usage example (From jQuery Docs site)

<html>
  <head>
  <script src="prototype.js"></script>
  <script src="jquery.js"></script>
  <script>
    jQuery.noConflict();
    // Use jQuery via jQuery(...)
    jQuery(document).ready(function(){
        jQuery("div").hide();
    });
    // Use Prototype with $(...), etc.
    $('someid').hide();
  </script>
  </head>
  <body></body>
</html>

You can also use the following code snippets to still use $() in your code, but with one drawback, you will not have access to your other library’s $() method.

// Method 1
jQuery(document).ready(function($){
    $("div").hide();
});

// Method 2
(function($) {
    /* some code that uses $ */ 
})(jQuery);

TIP:
Don’t forget that you can always assign jQuery to any other variable name to use it as your shorthand: var $_ = jQuery;

Identifying & locating mouse position in jQuery

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While writing the next jQuery tutorial I needed to identify and locate where the mouse was on the page. Tracking mouse position on the page with jQuery is easy. You don’t need to check what browser the script is running like it is used to be with plain JavaScript. To identify where the mouse is in jQuery all you have to do is to read event object’s .pageX and .pageY properties.

Example:

$().mousemove(function(e){
   // e.pageX - gives you X position
   // e.pageY - gives you Y position
});

The above jQuery code is binding a new ‘on mouse move’ event to the current document and triggered every time mouse moves. The coordinates are calculated in pixels from top left corner of the document. See the above code in action.

You may also want to know the coordinates of the mouse relative to some <div> or an element. Since jQuery returns mouse position relative to the document root, by subtracting element’s position from document root you get mouse positions relative to that element. Long story short here is the code to do just that:

$("#someDiv").click(function(e){
    var relativeX = e.pageX - this.offsetLeft;
    var relativeY = e.pageY - this.offsetTop;
});

Don’t forget that you can bind any mouse event to any element and then get mouse positions. You can easily create a draggable object with click and mousemove events by simply setting the CSS top and left values to .pageX and .pageY.

Anyway, that’s how you locate and handle mouse positions in jQuery. As always, you don’t need to worry about cross browser compatibility issues while using jQuery. To learn more see more examples here.

jQuery custom selectors with parameters

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My last tutorial on how to create a custom jQuery selector showed you the basics of creating custom filters in jQuery. Now, it is time to get more serious with selectors and create more advanced jQuery selectors – custom jQuery selectors with parameters. To get an idea of what I am talking about think of :contains(someText) selector.

Anyway, let’s create our own jQuery selector that takes arguments. The basic syntax is the same:

$.expr[':'].test = function(obj, index, meta, stack){
    /* obj - is a current DOM element
       index - the current loop index in stack
       meta - meta data about your selector !!!
       stack - stack of all elements to loop
   
       Return true to include current element
       Return false to explude current element
    */
};

meta is a parameter we are interested in. meta is an array that carries an information about our selector. Here is what it looks like:

$('a:test(argument)');
//meta would carry the following info:
[
    ':test(argument)', // full selector
    'test',            // only selector
    '',                // quotes used
    'argument'         // parameters
]

$('a:test("arg1, arg2")');
//meta would carry the following info:
[
    ':test('arg1, arg2')', // full selector
    'test',                // only selector
    '"',                   // quotes used
    'arg1, arg2'           // parameters
]

Here as you can see, we can make use of the arrays fourth (meta[3]) value to get a hang of our parameters.

Creating custom jQuery selector with parameters

Now, let’s improve our selector from previous post that selects all links with non empty rel attribute and make it select any element with specified non empty attribute. Here is the code to do just that:

$.expr[':'].withAttr = function(obj, index, meta, stack){
  return ($(obj).attr(meta[3]) != '');
};

See it in action here.

Find & select all external links with jQuery

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Selecting all external links and amending them in some way is probably one of the most used jQuery tutorials. By selecting all anchor links on the page and for example adding a CSS class with only one jQuery line shows how jQuery is simple and powerful. Also if you are progressively enhancing your website this is one of the trick you might use.

Actually, I had to select all external links and add an image that indicates it the other day. So, I created a custom jQuery selector called :external that makes finding external links easier for you. (Read “Custom jQuery Selectors” post to learn how to create your own custom selectors)

External links custom jQuery selector code:

// Creating custom :external selector
$.expr[':'].external = function(obj){
    return !obj.href.match(/^mailto\:/)
            && (obj.hostname != location.hostname);
};

// Add 'external' CSS class to all external links
$('a:external').addClass('external');

You can see this code in action here.

You may use the code above to:

  • Add CSS class to all external links
  • Dynamically add an image after the link to indicate that it is an external link
  • Bind a click event to track what links where clicked
  • etc.

Update: The return part was update to take into the account the mailto links as suggested in comments by Phillipp and Karl below.

Custom jQuery selectors

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jQuery makes it easy to select elements you need using CSS selectors. It is undoubtedly one of the jQuery features that makes it a great javascript library. On top of standard CSS selectors jQuery introduces some custom selectors that makes your code even more simpler and easier to read.

Examples of custom jQuery selectors are: :header, :even, :odd, :animated, :contains(text), etc.

And the best part is that jQuery lets you create and define your own custom selectors using custom selector creation template below.

jQuery Custom Selector Creation Template:

$.expr[':'].test = function(obj, index, meta, stack){
    // obj - is a current DOM element
    // index - the current loop index in stack
    // meta - meta data about your selector
    // stack - stack of all elements to loop
   
    // Return true to include current element
    // Return false to explude current element
};

// Usage:
$('.someClasses:test').doSomething();

Let’s now create a very simple custom selector using the template above. Let’s say we want a custom jQuery selector that will return elements with nonempty rel attribute.

$.expr[':'].withRel = function(obj){
  var $this = $(obj);
  return ($this.attr('rel') != '');
};

// Usage:
$('a:withRel').css('background-color', 'yellow');

The code above creates a custom selector that will select only elements with not empty rel attributes. Here is the above code’s demo page.

You might also be interested in reading about jQuery custom functions.

UPDATE: Read about creating custom jQuery selectors with parameters.