JScript Engine Improvements – IE8 beta.

In this post, I just wanted to lay focus on some of the improvements that have been done in the JScript engine shipped as a part of IE 8 Beta release. These improvements include:

·         Changes to the JScript Garbage Collector to reduce circular memory leaks

·         Optimization of String Concatenation and Other Built-In String Operations

·         Optimization of Built-In Array Operations

·         Execution Engine Optimizations, which include

o   Function Calls

o   Accessing prototype properties of an object

o   Specific look-up patterns for JScript variables via window.foo and this.foo, where foo is the variable and this represents the global window object


Details about changes made and the best practices for these areas are documented in the Platform Performance Improvements whitepaper. Other whitepapers related to the IE8 are available here.

Comments (3)

  1. In this post, I just wanted to lay focus on some of the improvements that have been done in the JScript

  2. If you have ever struggled to debug a JScript bug in Internet Explorer, you have a new friend – Developer

  3. rfink53 says:

    An oddball scripting bug/glitch resulting from IE 8’s new "adaptive" Zoom feature:

    The screen.width/screen.height/screen.top/screen.left properties no longer report the actual values when the page is zoomed. You get skewed "zoomed" values instead.

    (FF, Opera, don’t do this – this fails the interoperability test, for sure.)

    I would imagine this is going to mess up a lot of analytics out there with all sorts of weird screen resolutions being reported. Not to mention the positioning of pop-up windows on some sites? (Haven’t tested that one yet.)

    A "deviceX" and "deviceY" property or some such can be added, perhaps?

    IE8 seems to "see" the entire screen with the same zoomed pixel values it uses within the browser window.

    The same goes for IE’s built-in "Client Capabilities" behavior which also has width,height,top and left properties to query. Plus the screen.availWidth, etc… properties, too.

    This is the result, I assume, of IE8 moving from what they call an "optical" zoom feature in IE7 to an "adaptive" zoom feature in IE8.

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