Microsoft® JScript®
What Is JScript?
 JScript Tutorial 

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. This tutorial is intended to help you get started with JScript.
Easy to Use, Easy to Learn
JScript is an interpreted, object-based scripting language. Although it has fewer capabilities than full-fledged object-oriented languages like C++ and Java, JScript is more than sufficiently powerful for its intended purposes.

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.

JScript is a loosely typed language. That means you do not have to declare the data types of variables explicitly. In fact, you cannot explicitly declare data types in JScript. Moreover, in many cases JScript performs conversions automatically when they are needed. For instance, if you try to add a number to an item that consists of text (a string), the number is converted to text.

The rest of this tutorial is an overview of JScript features. For full details of the language implementation, consult the language reference.

Note  The code in many of this tutorial's examples is somewhat more explicit and less dense than code you'll find in actual Web pages. Most of it is also fairly simple. The intent here is to clarify the concepts, not to express optimal coding conciseness and style. There is, in any case, no shame in writing code that you can read and easily understand, six months after you write it.