Change Default Html Select Event

var lastValue = '';
$('selectbox selector').click(function(e)
 {
   lastValue = $(this).val();
 }).change(function()
 {
 changeConfirmation = confirm("Are you confirm to change the selection");
 if (changeConfirmation)
 {
    // Proceed as planned
 }
 else
 {
     $(this).val(lastValue);
 }
 });
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Jquery Image Preload

(function($) {
  var cache = [];
  // Arguments are image paths relative to the current page.
  $.preLoadImages = function() {
    var args_len = arguments.length;
    for (var i = args_len; i--;) {
      var cacheImage = document.createElement('img');
      cacheImage.src = arguments[i];
      cache.push(cacheImage);
    }
  }
})(jQuery)

jQuery.preLoadImages("image1.gif", "/path/to/image2.png");

source : http://engineeredweb.com/blog/09/12/preloading-images-jquery-and-javascript

Improve your Jquery Performance

Here is 25 excellent Tips that will improve your jquery performance.

1.  Load the framework from Google Code
2.  Use a cheat sheet
3.  Combine all your scripts and minify them
4.  Use Firebug’s excellent console logging facilities
5.  Keep selection operations to a minimum by caching
6.  Keep DOM manipulation to a minimum
7.  Wrap everything in a single element when doing any kind of DOM insertion
8.  Use IDs instead of classes wherever possible
9.  Give your selectors a context
10.  Use chaining properly
11.  Learn to use animate properly
12.  Learn about event delegation
13.  Use classes to store state
14.  Even better, use jQuery’s internal data() method to store state
15.  Write your own selectors
16.  Streamline your HTML and modify it once the page has loaded
17.  Lazy load content for speed and SEO benefits
18.  Use jQuery’s utility functions
19.  Use noconflict to rename the jquery object when using other frameworks
20.  How to tell when images have loaded
21.  Always use the latest version
22.  How to check if an element exists
23.  Add a JS class to your HTML attribute
24.  Return ‘false’ to prevent default behaviour
25.  Shorthand for the ready event

This article was orginally posted on http://www.tvidesign.co.uk/blog/improve-your-jquery-25-excellent-tips.aspx.