IE 9: First look at the new JS Engine

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The IE team is busy working on the next version of the world's most popular browser. IE 8 is the most widely used browser on Windows. IE 9 is currently in the oven and the IE team is ready to talk about what they're working on. Here, JavaScript engine team members John Montgomery, Steve Lucco and Shanku Niyogi give us an early look at the new JS engine that will ship with IE 9. As of the interview, it is on par with the latest performance numbers of the latest Firefox beta and making progress in catching up to Chrome's latest V8. Again, this is a really early look at where the JS engine is and where it's going (and what they've done, architecturally, to speed up IE's JS engine). Enjoy!



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The Discussion

  • User profile image

    Hey Now Charles,


    This was a very good vid! Really enjoyed it.


    Aside from JS improvements in IE9, your statements on the user experience is important which I'm sure we all agree & sure hope that there is the feature 'Speed Dial' which could be the best feature since tabbed browsing.


    Thx 4 the info,



  • User profile image

    @Charles: Complex computation in JS isn't any fun. I did PNG compression once... it was slow. You had to wait like 10-15 minutes for a file to save. It didn't run in a browser though.

  • User profile image

    I request someone from the IE team to please give a straight answer right away. Will IE 9 run on Windows XP SP3 and Windows XP 64-bit SP2? If yes, will the XP version continue to use GDI? How will DirectWrite and Direct2D for XP be handled bcoz there's no WDDM! You can't kill support for an OS that 70% of the installed base use.

  • User profile image

    For the love of God, it's 8 years old. Time to move to 7.

  • User profile image

    I think it's very unlikely that it will be supported in XP. It's an OS that's over 8 years old now. You shouldn't be using it any more. Wink

  • User profile image

    Remember IE9 is still probably 18+ months away.  The market share figures should be different by then (or at least Microsoft hopes they will be).  Besides, people who are OK with sticking with XP are probably OK with sticking with IE8 (or other browsers).

  • User profile image

    All I want to know is, well we have a proper tab switching experience? Meaning, can I switch tabs while the stuff inside a tab is not responding?


    Can we actually have a default download directory setup as a string, like Home Page URL? What I mean is, we always have the same home page until we specifically change it, can we just have the same dumb easy thing on download directory? I think it is annoying when the directory keeps changing based on the last download, it is more complex in code and harder for users to use.


    Spell Check please, oh man.


    And I really think they need to change the GUI design to release more vertical spaces.


  • User profile image

    That's not really for a thread about the Javascript engine. But while we're off-topic, I'd like to commend on the new inteerview style where there's a separate cameraman, it looks very dynamic and engaging Smiley


    A couple of complex processing examples...


  • User profile image

    Would someone please ask that guy to refrain from the overuse of the phrase "Right On"?



  • User profile image
    Ryan Kearney

    And what are the odds IE9 will pass the Acid 3 test?

  • User profile image

    This also shows how un-interesting most user look at JS Engine. We don't care it when the tabs are freaking slow and stucked. The end user experience is more imporant here because it is an end user product.


  • User profile image

    Well, IE9 looks like something I'd want to use. Until then Firefox + Chrome will be used. Is the release for IE9 really 18 months from now? That is insane.

  • User profile image

    Haha, yeah... and people who are "OK" with IE7 are running Windows 2000.

  • User profile image

    so, why isnt ie9 leveraging the dlr for js?


    as for speed, it can never be to fast imo Smiley

    consider using the canvas element i html5, thats a big speed sink i think

    but then again, why anyone would use the canvas element when there is silverlight, i dont know Wink


  • User profile image

    It was said that the JavaScript Engine generates "native code". Is this something that utilizes the DLR, or did you guys write a completely new JavaScript compiler?


    Also, what is the possibility that this new JavaScript Engine could be exposed as an API to be consumed by other applications? Yeah, you could always embed the Web Browser control, but what about accessing just the JavaScript Engine?

  • User profile image

    honestly, all ppl really care about is whats the forced migration plan to put a knife in ie6 and 7 for good. developers, developers, developers.

  • User profile image

    Will IE9 break older Javascript Frameworks? I'm still using an older mootools and jQuery (not most recent)

  • User profile image

    Soo, jscript was equiv of js1.5 even in ie8, is there any improvements here? iterators (and so on).

  • User profile image

    So are there any plans to move away from the JScript dialect and embrace some of the more modern aspects of JavaScript 1.5 and beyond? Like getters and setters, or lambda/concise functions?

  • User profile image

    Very interesting video. I would have liked them to run something from Chrome Expirements, as many of the demos on the site don't work in IE8 and make heavy use of JavaScript.

  • User profile image

    I asked for a straight answer but apparently no one at Microsoft cares about XP users or is competent enough to answer. I'm sticking with XP because I can't work with the horrible Windows Explorer in Windows 7. See and

  • User profile image

    Theres absolutely no reason why they would backport this to xp, you can 'HEART HEART HEART HEART 4EVA' xp all you want, and blabber on about how the new windows is aparently worse.. but the fact is that theres a pretty big care factor for microsoft, xp is now to become extremely legacy given it is now two revisions behind, and approaching 10 years old..


    Not many improvements they've made will run on xp, the d2d stuff for example.. if you want the latest software they uh.. you should consider the fact you may need the latest platform.. or hell, at least one made in the last 5 years... ie vista.


    To summarize: your petty issues with not wanting to upgrade != issues why microsoft should backport a crippled version of ie9 to xp.


    And from a user/dev's perspective, I don't want microsoft to be spending their time (which for IE is extremely short IMO), trying to get the latest in software to work on the quirky and old.

  • User profile image

    You do realize that the legacy petty OS that you are bashing still as of today right now runs on 65%+ of the world's computers right? Also web developers want less different versions to develop for.


    And how old XP really is doesn't matter, it is just 2 releases behind (but one of the releases was the most badly received one in the history of MS OSes and the other is a minor refresh of the one that failed). XP received a major update equivalent to a full release in 2004, is supported with patches, dominant in the enterprise, has no issues, and remember MS released IE6 for Windows 98 as well and IE 5.5 for Windows 95.

  • User profile image

    I have always been annoyed when channel 9 videos don't provide everyone with a microphone.... come on people.

  • User profile image

    IE8 is currently the best web browser overall. However, there is scope for improvement. As a tech blogger and as an ordinary user, I very much look forward to IE9.

  • User profile image

    IE7 and IE8 have not shifted any huge numbers from IE6.. if you look at the statistics for IE, and Windows, you see that IE6 pretty much matches up to the amount of XP users.. web developers don't think aw god nother browser to worry about.. web developers want to generally stay in a happy middle ground where we can use modern enough features, and perhaps stick our necks out of newer features when its sensible to do so.


    IE6 is uniquely the only browser web developers REALLY worried about, it is SO FAR behind todays browsers you stand little chance of making a modern site that can be tweaked to work ok in IE6.. any other modern browsers may disagree on small things, but these are things that are generally easy to fix..


    If you are including IE6 support in your site then the approach you take to building the html/css is COMPLETELY different, you try to avoid anything at all complicated.


    I'd also like to point out the immense level of piracy that XP received, to the point today people expect to pick it up for nothing on a torrent site, I'd say theres a noticable percentage of that XP base that are still there purely because they are of the false expectation that an OS should be FREE to them, and are finding it impossible to successfully pirate newer versions of windows.


    These are certainly not people I care to support, nor should microsoft, nor should microsoft after two versions of windows be trying to 'make happy' the people that * and moan the newer revisions aren't up to scratch.. they will NEVER make you happy because your expectations for what an OS should be are unrealistic and twisted, and completely the opposite of any vision microsoft has.


    So in short you can get screwed, stick to your OS that will see increasingly smaller product releases/updates, or move to a new OS, whatever OS you want.


    Ofc Microsoft won't say this, they have to keep up the PR and smile and convince you to upgrade to their latest OS, but again expect that to become increasingly 'old' for them to keep up.

  • User profile image

    What I'm expecting to see is that IE9 would implement ES5, as the result of "Harmony" of EcmaScript. If that becomes real, we'll be getting a few more modern JavaScript features.

  • User profile image

    It will actually be more like 2.5 releases behind by the time IE9 is released, since MSFT will be well into Windows 8 development by then.  That would go further back than any previous release of IE has gone with OS support.

  • User profile image

    Mozilla and Google is going to support Windows XP for as long as it has substantial marketshare. It's a nonissue really.

  • User profile image

    "if you look at the statistics for IE, and Windows, you see that IE6 pretty much matches up to the amount of XP users"


    Where are you getting your numbers from? IE6 is at 23% here: and Windows XP is in the 60-70% range that is 2/3 of the market. Do you not see any difference between 23 %  and 60%? MS has never announced IE9 won't be there for XP. It's the same reason MS is still producing Office 2010 for XP users. The only question is whether it'll continue to use GDI which my guess would be Yes. Other browser vendors may well offer hardware accelerated rendering on XP as well using OpenGL. MS don't want to lose marketshare and the web "battle" against Google.

  • User profile image

    Office 2010 = 2010

    IE9 = 2011

  • User profile image

    Well, let's hope life with IE related development will be easier in the upcoming years Smiley.


    Default download directory is so simple but again so easy and good Smiley





  • User profile image

    Wow after reading about the set download directory, that made me want to have that really bad.


    On top of that though we need to have the IntelliPoint accelerated scrolling issue fixed.  Also faster opening tabs would be great!

  • User profile image

    I hope you improve the interface too.


    - Opening a new tab seems too slow.

    - Password save confirmation dialog stops page load.

    - I want more IU configuration options (e.g. min tab size on the tab bar (to allow more tabs fit in my screen), make Ctrl+S open the save page dialog).

    - All new tabs should open right next to the current one (or provide an option for that). Now they don't.

    - A new way to save and load named browsing sessions (the current always makes me lose my last browsing session and can't save multiple. IEPro's session manager doesn't work). If you could also add a way to pick a web page from any saved session in order to place it to your current session, you would make many users happy.

    - Make IE remember the last saving format (HTML/MHT - when saving web pages on disk) and the last saving directory selected ny the user. Also an option for whether or not to always save in a default location would be nice. Also, an option to make IE automatically change the name of the file to be saved (appending numbers - like Chrome does) when the file name already exisits (and the save dialog is used) would be more than nice.

    - Make a build-in configurable download manager (or a small, light add-in for it -- IE Pro causes problems to me).

    - Add a "tab manager" similar to Chrome's "task manager".

    - Make sure that saving a page on the disk is not slow (it is now...) and that it doesn't prevent you from working with IE during it's execution.

    - Sometimes IE crashes and killing it using Task Manager is impossible (you have to restart the PC). Provide a way to do so (if possible).

    - Make a build-in check speller (or better provide a small simple light addin for it -- IE Pro causes problems).

    - Put a "paste and go" option on the context menu showed when you right click in the address bar.

    - Add a "go to URL" option on the context menu showed when you right click on selected text in a web page.

    - Cooperate with IE7 Pro team and, perhaps, use their work.

    - Make the "stop page load" button get disabled when loading is done or merge this button with the refresh button.

    - Making it possible for users to use more that one version of IE on a single system would be great.

    - I don't know how the saved passwords are being saved and protected, but a master password protection would be safer. It would be great if you could make a password manager similar to the one used in Opera.

    - Despite the fact that IE and Chrome are supposed to use the same tab technologies, Chrome is responding MUCH better. Could you make IE's code in the instance of IE that holds the tabs run faster or parallelize routines to avoid lack of window response ?

    - And the MOST IMPORTANT: Sometimes IE fails to load some elements in a web page (I guess) and disconnects from the web (with all sorts of annoying pop up windows that appear). Then you have to connect again (as notified and asked by another window) to continue browsing. Can you please eliminate all of these pop up windows ? I mean only your browser annoys the user with so many pop up windows. Why do we get disconnected in the first place ?


    You did a good job with the search box, the duplicate tab option, the reopen closed tab option, etc !

    Keep up please.

  • User profile image

    Would love to know about the DLR story here.  Are these optimizations specific to JavaScript, why not all work on the same runtime performance though the DLR.  It may mean going to IL first - but this would have other added benefits, like improved interop with Silverlight.

  • User profile image

    Dean actually answered this exact question during our C9 Live conversation at PDC09. You'll be able to watch that interview soon. Well, now.



  • User profile image
    Leon Sutton

    To all of those arguing over the necessity (or non-necessity) of making IE9 compatible with Windows XP, I'd like to remind you all that Microsoft officially announce a year or two ago that they'd soon discontinue product support for Windows XP. Guess what that means ... while this browser may be supported in Windows XP, future browsers will most assuredly not be supported in it.
    I personally believe we should stop development for legacy platforms and look ahead to the future ... and not just from a Web developer's standpoint, either. Remember that developing for legacy platforms, regardless of the development technology, overbloats and overwhelms the overall development process and extends the development time exponentially. Wouldn't it be grand if we can write an application exactly one way and be able to distribute it among several different platforms, thus leaving the choice of platform entirely up to user preference?
    That's all I have to say about that.
    I'd like to give an, "Awesome job so far," to the developers of IE9. :)

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