|JScript 1.1||No||Never released|
|JScript 1.2||No||Evidence of its existence but status unknown|
|JScript 2.0||No||Released with IIS 1.0|
|JScript 4.0||Yes||Released with Visual Studio 6.0|
|JScript 5.1||Yes||Released with IIS 5.0 on Windows 2000|
|JScript 5.5||Yes||Released with MSIE 5.5|
If the JScript interpreter is re-installed without upgrading the browser, you may be using a version of JScript that is later than the browser. Scripts should work normally as long they do not exploit features of JScript that have changed. However, the scripts may not be able to access some new features of the later version. For example, JScript 5.5 can be installed over the top of JScript 5.0 in a version 5.0 MSIE browser. You get the later core language features but continue to use the old document model. This can get utterly confusing for script developers.