What’s New in JScript for IE8 Beta 2

One of the key themes for IE8 is developer productivity. IE8 Beta 1 improved developer productivity through an optimized core scripting engine and script debugger. In this release, we continued to invest in the areas that bring more power and productivity to the web developer community. Here is a quick summary of the work that we’ve done for IE8 Beta 2:

Scripting Engine

Many enhancements have been done to the scripting engine. One feature that will bring a lot of value to the AJAX developers is the introduction of native JavaScript Object Notation (JSON). With JSON becoming the de-facto data interchange language for contemporary web applications; we have included native JSON support within the JScript engine. With this, developers can use a native JSON object to serialize and de-serialize JScript objects. This feature makes Internet Explorer 8 the first browser to support JSON natively!

Script Debugger

You have experienced the script debugger in IE8 beta 1. We’ve made it even better in IE8 beta 2. You can view script in syntax colored code similar to what you might expect in code editors such as Visual Studio™. The console shows all the script errors in a webpage at a central location. We also support the console.log mechanism to log the errors effectively. The Console is extensible for you to add your own commands through custom scripts.

Script Profiler

This is one of the new features of the IE8 Developer Tools. It will help you identify and fix performance bottlenecks in scripts so that they can run better and faster. The Script Profiler comes with an easy-to-use UI and powerful features such as ‘Call Tree View’ and ‘Export’ functionality. The Profiler output can be exported to tools like Excel so you can visualize the execution times through charts and graphs.

Does this sound interesting? Check out the JScript PM Channel 9 video to learn more. Stay tuned for more in depth details on these features in future posts.

Shreesh Dubey
JScript Team
Product Unit Manager

edit: title adjustment

Comments (24)

  1. Les says:

    Before somebody else gets all nit-picky/pedantic, it’s worth pointing out there’s a JSON object in Firefox as of at least 3, but I think it’s only available for extensions to use (http://developer.mozilla.org/en/NsIJSON). In other words, useless to web developers.

    Technically, it’s possible if your visitors have signed.applets.codebase_principal_support set to true and your code asks for and recieves UniversalXPConnect, but that’s dangerous and unrealistic.

  2. -TNO- says:

    According to bugzilla, Firefox 3.1 and JavaScript 1.9 will include this….So i guess its a game on who releases first? Comparing betas to betas is quite a gray area I would think

  3. JackyMao says:

    As I looked through all these FEATURES, I can’t say this is what I want!

    You IE team just always make things too TECHNIC, you need to add something new, something really exiting people. so that people can turn to IE & say "you see, the new IE is really exiting." you need to make people surprise & admire, but not just say by your self,"Does this sound interesting?" No!

    Let me tell you what can make people surprise, at least in China.

    1. You can make an website, that can support IE very good, but do not support other browser so well. Put MUCH MORE interesting pages in this website. & Show to people how IE is interesting. Try to give people a surprise! & admire! Do not just do as your TECHNIC brain think!

    2. Develop something that can make people develop their own page just in IE, they can rebuild whatever interesting page they like, & use for their own site. If possible, make the ie can connect to a database, sql server or mysql or something.


    That’s all for now, just make IE simple, & attactive. No TECHNIC.

    I am in expectation that IE can do something wonderful, so I post here.

  4. Is IE 8 going to support prototyping on DOM objects like elements? That would help us pull off interim solutions to some of IE’s other DOM shortcomings.

  5. Any word if the enhancements include (or will include) support for the RFC 4329 MIME types (i.e., |application/javascript| and |application/ecmascript|)? (On that topic, it would also be nice if the correct MIME type for XSLT was supported (i.e., application/xml).)

  6. Patrick Garies: Ah, I missed that bit. Thanks, great news!

  7. Joe says:

    I still live in hope that they’ll solve the design flaw of not being able to append to the DOM before the page reaches complete state, like all other browsers in existence allow you to do, but IE gives you "Internet Operation Aborted Error". Yes I know there was another blog post about this, but it’s clear the IE team still think this is not their error. They think it shouldn’t be allowed, and that downgrading it from the equivalent of a BSOD for a browser, to just an exception that can be handled, is the answer. No it’s not. It’s still not doing the job we want it to.

    So I’ll still need a logic branch to handle IE needing to wait before I can dynamically create elements, whereas the else (being ALL other browsers) can go ahead and add without fear.

    This is the most important problem IE has for me, and even IE8 isn’t going to solve it.

  8. I think that these are very good improvements. I think that the greatest benefit will be for developers of Internet sites.

  9. Olivier says:

    @JackyMao : your suggestions are very wrong :-/

    We want that ALL browsers works the same on EVERY websites.

    So why suggesting to make a website which only works with IE ? That’s not the way to get new users.

    The differences between browsers should only be the user interface, the speed, customizations,… stuff like that, but the rendering should be exactly the same.

  10. Jim Green says:

    as said, js would become more important in the future internet application. I do think so.

    ie should provide more convenient and rich js error control for developers.

  11. Mike says:


    If you want to see something new and useful check out Firefox3.1 alpha2

    Support included for the HTML5 <audio> and <video> tags. These should have been around for a long time.

    One day maybe, people will be able to go over to watch the channel 9 video in their browser without having to install Silverlight.

    (to be fair you can download it)

  12. Thanks for making these important changes.  Hopefully IE continues to gain in performance and by making it much easier for us as developers its a good change to see.

  13. C’est ce qu’annonce, entre autres, le blog de MSDN dans un billet consacré aux nouveautés de JScript (le JavaScript à la sauce IE) dans la bêta 2.

  14. Haw-Bin Chai says:

    Is it just me, or did javascript performance see a huge speed boost in beta 2 over beta 1?

    The profiler is a killer feature that I’ve been wanting for a long time. Some areas need polishing – the "Line Number" does not appear to be accurate (always displays "1" in my test), and it’s pretty important to be able to uniquely identify the functions being listed (i.e. by their object scope). Still, this is awesome stuff.

    Great job IE8 team, keep the good stuff coming!!!

  15. JackyMao says:

    @Olivier  Thanks for your reminding, I just mean IE need some new way to get new user. NEW way. Not just walk away in this single way.

    @Mike  Thanks, I am using Firefox also, competition can make IE & Firefox move on.

  16. Olivier says:

    @JackyMao : yes, I agree with you that new ways to get new users are needed.

    What I meant was to fix problems first, then of course, if they have time they can create new interesting features (like they already did with the Accelerator and Webslice).

    PS: I’m a web developer, that’s why I think fixing rendering bugs is much more important than anything else 🙂

  17. Mitch 74 says:

    Are there still fixes planned? Because in IE 8 Standards mode, when using CSS pseudoframes (say, a fixed size, absolutely positioned, scroll:auto div), if a page element has an even handler (mychild.attachEvent("onclick",myfunction} for example) which triggers some DOM modification (innerHTML and appendChild work) then the pseudoframe scrolls back to top (focus doesn’t change).

    The listener element and modified element don’t have to be children of the pseudoframe to trigger the ‘scroll to top’ bug.

    I’ve successfully triggered the bug with key (-press,-down,etc.) and mouse (-over,etc.) listeners.

    Basic page exhibiting the bug: http://www.moneyshop.fr/testscroll.html

    Same function used with W3C event structure, no problem in Firefox/Opera/etc.

    To use, scroll the pseudoframe a bit, then hover the top paragraph: instant reset.

    Any idea on a bugfix? Current workaround is to fallback to IE7 mode – which I don’t want (other IE 8 bugfixes allow me to forgo a lot of compatibility CSS code).

  18. Mitch 74 says:

    erratum: I meant: ‘overflow:scroll’ of course (or, as is the case of the example, overflow-y:scroll).

    addendum: using CSS DOM modifications (with :hover:before for example) triggers the bug too, as well as the Netscape legacy event model; as such, I’d say any DOM modification entails a reset of all pseudoframes scrolls on the page.

    Test case has been updated.

  19. Sean Cameron says:

    How about significantly better garbage collection, and actually cleaning up when the WebBrowser control is destroyed? I realise that this refers to the OCX rather than IE8 itself, however at the moment the WebBrowser control leaks enormous amounts of memory, even when nothing is loaded into the control. This is trivially reproducible in both managed and unmanaged code, in single and multi-threaded applications. It is even worse with pages that use JavaScript, somewhere along the line cleanup is simply not being done, as almost all allocated memory is leaked. I have reproduced this, but there seems to be no avenue to actually report the issue to the IE8 Beta team. I eventually reported it to the Visual Studio .NET framework team, who closed the bug, as it is not directly related (which is fair enough): https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=362973&wa=wsignin1.0

    I sincerely hope that something is done about this, as it is a show-stopper when it comes to using the WebBrowser control.

  20. JScript Blog says:

    In Internet Explorer 8 Beta 2 JScript team has focused on improving developer productivity. You can read

  21. IEBlog says:

    During Beta1 and Beta2 pre-releases of IE8, we’ve blogged about the performance optimizations done in

  22. JScript Blog says:

    During Beta1 and Beta2 pre-releases of IE8, we’ve blogged about the performance optimizations done in

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