I should mention up front that jQuery was an indispensible tool when I was working on this project as in many cases I was able to replace the offending JavaScript with a jQuery equivalent that was cross browser compatible. If you’re a web developer and are not familiar with jQuery, you probably should be.

So a couple of things to look out for… I wanted to list the easiest ones to spot first as you can do a text search and usually find all of them:

1. CSS Expressions:
   • Were implemented in IE5 and allow you to assign a JavaScript expression to a CSS property.
   • Were deprecated in IE8 standards mode, see http://blogs.msdn.com/ie/archive/2008/10/16/ending-expressions.aspx for details.
   • IE specific.
   • Search for: “expression(”
   • Replace with JavaScript that dynamically modifies the CSS properties in response to specific browser events (onresize, etc).
     • In many cases this can be more performant than CSS expressions because you can choose to bind to specific events (CSS expressions are reevaluated *every* time a JavaScript event with at least 1 listener fires.
2. outerHTML:
   • “Get or set the HTML of the entire node x, including the outermost tag (element x itself).”
   • Example: x.outerHTML = “Let’s <u>change</u> it!”
   • IE specific.
   • Search for: “outerHTML”
   • Replace with innerHTML or W3C DOM methods. innerHTML is in theory faster, but IE and Konquerer have some issues when innerHTML is used with tables. Replacing outerHTML with calls to innerHTML will also require some changes to the logic using outerHTML as innerHTML is slightly different in behavior.
3. Visual Filters:
   • Used commonly to create gradients without using images.
   • More information on Visual Filters: http://msdn.microsoft.com/en-us/library/ms532853.aspx
   • IE specific.
   • Example: <ELEMENT STYLE=”filter:progid:DXImageTransform.Microsoft.Gradient(sProperties)” … >
   • Search for: “DXImageTransform”
   • Replace with… Unfortunately there really isn’t an equivalent for this. Some of the visual filters can be replicated using standard CSS properties, but not all of them. As convenient as the visual filters are, they will only work in internet explorer at the moment.
4. Window.Event:
   • Used to access JavaScript event information in IE.
   • IE Specific.
   • Search for: “window.event”
   • This item could have several pages written about it, but the short story is that IE handles passing JavaScript event information differently than other browsers. You will need to code your JavaScript to accommodate this difference. jQuery can again be useful here as it can abstract a lot of this problem away from you. I recommend reading the section on events here: http://www.reloco.com.ar/mozilla/compat.html as it will give you an overview of the problem and how to address it.
5. Custom Attributes:
   • Used to defined custom element attributes.
   • Getting or setting custom attributes without using DOM methods is not cross browser compatible.
     • Example: element.MyProp = “This doesn’t work in all browsers.”
   • Search for… No good search string for these. You just need to keep your eyes out for JavaScript that makes calls to custom attributes without using DOM methods (or jQuery).
   • Replace with: calls to .getAttribute(“MyProp”) or setAttribute(“MyProp”) or if using jQuery, element.attr() as shown here: http://docs.jquery.com/Attributes/attr.

This list is by no means exhaustive, but I wanted to point out many of the common issues I have come across. Your mileage may vary. I recommend checking out the references listed below for a lot more good compatibility information. I’ve tried to check all of my facts, but if you notice anything that seems off, let me know so I can fix it!

References:

• http://www.reloco.com.ar/mozilla/compat.html – “Making your web browser compatible with Firefox”
  • A good overview of many of the common browser compatibility problems faced when making an web app written for IE work in Firefox
• http://www.quirksmode.org/compatibility.html – “Compatibility Master Table”
  • The holy grail of browser compatibility information. Seriously… Want to know if a browser fully supports CSS2, CSS3, DOM, etc? It’s here.
• http://reference.sitepoint.com/ – “CSS/HTML/JavaScript Reference”
  • Reference site for CSS, HTML, and JavaScript information. Its got a clean layout and additionally contains browser compatibility information for each of the items.
• http://blogs.msdn.com/ie/archive/2009/03/12/site-compatibility-and-ie8.aspx – “Site Compatibility and IE8”
  • A page detailing potential issues and fixes for making your pages compatible with IE8 in Standards Mode. This is actually a good reference for potential cross browser problems as most of the items listed are cross browser compatibility issues as well.

The official 1.3.0 documentation was posted this weekend as well and is also available from the downloads link above, or this Google Code download page.

Keep your eyes peeled for a jQuery 1.3.2 release anytime in the next few days as John Resig has mentioned there is still one last 1.3 regression they are working on fixing.

For those interested, the regression has to do with the $(document).ready() function waiting until images are fully loaded in Internet Explorer 6 & 7. The jQuery bug ticket ID is #3988 and here’s a Stack Overflow question in which John Resig talks about the issue in some detail.

The blog post regarding this release makes a few important points to be aware of:

• jQuery support for Safari 2 is being phased out. 
  • Safari 2 has been superceded by Safari 3 and no longer has an appreciable market share.
• Packed versions of jQuery will no longer be available.
  • Packed scripts make debugging more difficult, cause platform incompatibilities (e.g. Adobe Air, Caja), and can actually increase loading times in many cases versus a plain minified script.

This update should not contain any breaking changes. Happy jQuerying!

Happy jQuerying!

I blogged previously about this release and the performance enhancements it’s expected to bring, but the release notes spell out in detail the performance differences of the new selector engine.

Along with this release, jQuery has created a new API Browser at http://api.jquery.com that is available in addition to the existing jQuery docs site. Whats nice about the new api browser is it can be downloaded and installed as an Adobe Air application.

Happy birthday jQuery!

John Resig mentioned in a podcast with Scott Hanselman a few months back that one of the primary goals of the 1.3 release was to increase performance and a quick glance at the important changes listd in this release, specifically rewrites of big parts JQuery like the selector engine, seem to allude to this.

A quick run of the Javascript library benchmark app at http://experiment.bcse.info/slickspeed/ on my machine using Chrome shows a *significant* performance increase in JQuery 1.3b1 versus 1.2.6 (final time of 13ms compared to 26ms, so about a 100% speedup overall).