On the Macintosh, MSIE 3.0 had no JScript, but version 3.01 did. That included JScript 1.0, but not the identical version as on Windows; there were differences between the Mac and Windows versions of JScript (for example, the Mac version supported the Image object for mouse rollovers, while the Windows JScript 1.0 did not). In 2003, Microsoft discontinued MSIE for Mac, ending official support in 2005.
Some versions of Windows are also associated with particular JScript versions (JScript is one of the scripting languages that can be used to script Windows itself). Windows 2000 shipped with JScript 5.1. Windows ME contained JScript 5.5, and Windows XP uses JScript 5.6.