JScript is Microsoft's dialect of the ECMAScript standard that is used in
Microsoft's Internet Explorer. JScript is implemented as an Active
Scripting engine. This means that it can be "plugged in" to OLE Automation
applications that support Active Scripting, such as Internet Explorer,
Active Server Pages, and Windows Script Host. It also means such applications
can use multiple Active Scripting languages, e.g., JScript, VBScript or
PerlScript. JScript was first supported in the
Internet Explorer 3.0 browser released in August 1996. Its most recent version
is JScript 9.0, included in Internet Explorer 9.
JScript 10.0 is a separate dialect, also known as JScript .NET, which adds
several new features from the abandoned fourth edition of the ECMAScript
standard. It must be compiled for .NET Framework version 2 or version 4, but
static type annotations are optional. Comparison to JavaScript
As explained by JavaScript guru Douglas Crockford in his talk titled The
JavaScript Programming Language on YUI Theater,
[Microsoft] did not want to deal with Sun Microsystems about the trademark
issue, and so they called their implementation JScript. A lot of people
think that JScript and JavaScript are different but similar languages. That's
not the case. They are just different names for the same language, and the
reason the names are different was to get around trademark issues.
JScript supports conditional compilation, which allows a programmer
to selectively execute code within block comments. This is an extension to the
ECMAScript standard that is not supported in other JavaScript
implementations. Versions
= JScript= The original JScript is an Active
Scripting engine. Like other Active Scripting languages, it is built on the
COM/OLE Automation platform and provides scripting capabilities to host
applications. This is the version used when hosting
JScript inside a Web page displayed by Internet Explorer, in an HTML
application, in classic ASP, in Windows Script Host scripts and several other
Automation environments. JScript is sometimes referred to as
"classic JScript" or "Active Scripting JScript" to differentiate it from newer
.NET-based versions. Some versions of JScript are available
for multiple versions of Internet Explorer and Windows. For example,
JScript 5.7 was introduced with Internet Explorer 7.0 and is also installed for
Internet Explorer 6.0 with Windows XP Service Pack 3, while JScript 5.8 was
introduced with Internet Explorer 8.0 and is also installed with Internet
Explorer 6.0 on Windows Mobile 6.5. Microsoft's implementation of ECMAScript
5th Edition in Windows 8 Consumer Preview is called JavaScript and the
corresponding Visual Studio 11 Express Beta includes a “completely new”,
full-featured JavaScript editor with IntelliSense enhancements for HTML5 and
ECMAScript 5 syntax, “VSDOC” annotations for multiple overloads, simplified DOM
configuration, brace matching, collapsible outlining and “go to
definition”. JScript is also available on Windows CE.
The Windows CE version lacks Active Debugging.
= JScript .NET= JScript .NET is a Microsoft .NET
implementation of JScript, it is a CLS language and thus inherits very powerful
features, but lacks many features of the original JScript language, making it
inappropriate for many scripting scenarios. JScript .NET can be used for
ASP.NET pages and for complete .NET applications, but the lack of support
for this language in Microsoft Visual Studio place it more as an upgrade path
for classic ASP using classic JScript than as a new first-class language.
JScript .NET is not supported in the .NET Compact Framework.
Note: JScript .NET versions are not related to classic JScript versions.
JScript .NET is a separate product. Even though JScript .NET is not supported
within the Visual Studio IDE, its versions are in sync with other .NET
languages versions that follows their corresponding Visual Studio versions.
.NET Framework 3.0 and 3.5 are built on top of 2.0 and do not include the newer
JScript.NET release. (Source: file version of jsc.exe
JScript.NET compiler and Microsoft.JScript.dll installed with
.NET Framework) See also
JScript.Encode Windows Script File
Windows Script Host Notes
References External links
JScript documentation in the MSDN Library
JScript 5.7 Release Notes JScript .NET documentation in the MSDN
Library JScript blog
JavaScript - JScript - ECMAScript version history
jPaq - A Fully Customizable JScript Library