"Microsoft JScript is a powerful scripting language targeted specifically for the Internet.
It is implemented as a fast, portable, lightweight interpreter for use in World Wide Web browsers and other applications
that use Microsoft ActiveX Controls, Automation servers, and Java applets. ...
JScript is the Microsoft implementation of the ECMA 262 language specification.
It is a full implementation, plus some enhancements that take advantage of capabilities of Microsoft Internet Explorer.
JScript is not a cut-down version of any other language (it is only distantly and indirectly related to Java, for example),
and it is not a simplification of anything. It is, however, limited.
You cannot write standalone applications in it, for example, and it has little capability for reading or writing files.
Moreover, JScript scripts can run only in the presence of an interpreter, either in a Web server or a Web browser." (Microsoft)