This is my second posts about jQuery Tips and Tricks. If you missed my first post, you might want to read it now useful and handy jQuery Tips and Tricks. This time, I found some performance tuning, element manipulations tips and tricks that I believe will able to help you develop a more effective and efficient jQuery script. Enjoy!

1. No conflict-mode

To avoid conflict when you are using multiple libraries in a website, you can use this jQuery Method, and assign a different variable name instead of the dollar sign. Using jQuery with other libraries

var $j = jQuery.noConflict();
$j('#myDiv').hide();

2. Total of selected elements

It return the number of elements that are selected by jQuery selector. Using length method will return the size of array which is equal to the number of selected objects.

$('.someClass').length;

3. Let Google host jQuery for you

There are advantages to let Google host jQuery. Some of us may not know, it actually provides better caching, increase parallelism and decreased latency compared with hosting it locally. Find out more about it: 3 reasons why you should let google host jQuery for you

<script src="http://www.google.com/jsapi"></script>
<script type="text/javascript">
google.load("jquery", "1.2.6");
google.setOnLoadCallback(function() {
    //Code to be inserted in this area
});
</script>

/* the best way (fastest and most efficient implementation) */
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js"></script>
<script type="text/javascript">
  $(document).ready(function() {
    //This is more like it!
  });
</script>

4. Check if checkbox is checked

jQuery provides us 3 ways to determine if a checkbox is checked. How to check if checkbox is checked

// First way 
$('#checkBox').attr('checked'); 

// Second way 
$('#edit-checkbox-id').is(':checked'); 

// Third way 
$("[:checkbox]:checked").each(
    function() { 
       // Insert code here 
    } 
);

5. How to disabled/enable an element with jQuery

// To disable 
$('.someElement').attr('disabled', 'disabled'); 

// To enable 
$('.someElement').removeAttr('disabled'); 
// OR you can set attr to "" 
$('.someElement').attr('disabled', '');

6. Improving jQuery code performance

Selecting an element using ID is faster than selecting classname. jQuery Performance Analysis of selectors.

update: apparently, jQuery 1.3 has a big improvement on this. So, I guess this tips only suitable for old browsers and jQuery 1.2 or below. Thanks Karl for the information.

/* ID */
$("#myid").html();

/* is faster than class*/
$(".myclass").html();

If you use a classname, the jQuery will perform better if you attached the element to the class name. A good practise when selecting a class:

$("ul.myclass");

/* is faster than this*/

$(".myclass");

7. Javascript Error Checker

Debugging javascript script can be extremely time consuming. So, if you running out of ideas what is causing the errors, you can use this free online tool JSLint

8. Disable jQuery animations

This will disable all jQuery animations if it's set to true.

jQuery.fx.off = true;

9. IE Rendering problem in fadeIn effect

If you used the fadeIn effect in ie6 before, you probably able to notice how urgly it looks. The text doesn't render the way it should. To solve this, you need to remove the filter attribute

// This causes this text glich
$("#message").fadeIn();

// This will fix it
$("#message").removeAttr("filter");

10. Check if jQuery.js is loaded

/* Method 1 */
if (jQuery) {  
    // jQuery is loaded  
} else {
    // jQuery is not loaded
}

/* Method 2 */
if (typeof jQuery == 'undefined') {  
    // jQuery is not loaded  
} else {
    // jQuery is loaded
}

11. Add an icon for external links

This trick is pretty simple and good for usability. If links are linking to external website, an image will be displayed next to the link. Dynamically add an icon for external links

$(document).ready(function() {
  $('#extlinks a').filter(function() {
 return this.hostname && this.hostname !== location.hostname;
  }).after(' ');
});

MORE TIPS AND TRICKS ARE WANTED!

I hope this list will able to help you. If you have some tips and tricks that you want to share with all of us. Please leave in comment. : ) Thanks!

Reference
jquery-howto.blogspot.com
How to Decrease Server Issues from Web Hosting Search
learningjquery.com