What is JavaScript?

Client-Side (vs. Server-Side)

JavaScript is a Client-Side language, which means the code is sent through the Internet to the user's computer. All of the JavaScript commands run on the user's computer, not on the Server.

 

Scripting Language (vs. object-oriented programming lang.)

JavaScript is not intended to be a full featured programming language to compete with C++ or Java. While some advanced techniques may be supported, JavaScript was created as a tool to add interactivity to HTML pages.

 

Interpreted (vs. Compiled Code)

An interpretted language is executed line-by-line by the computer that loads the page (see Client-Side above). The advantage to Interpretted languages is that the same code might be usable on a variety of machines (JavaScript will run in Netscape, IE, Mozilla, and Opera on a PC, Mac, Linux, or Unix computer). The down-side is that interpretted code runs slower as it has to be turned into instructions specific to the CPU and operating system on a line-by-line basis. A compiled program is already interpretted before it is downloaded - but generally must be recompiled for each CPU/OS combination.

 

Other Client-Side Scripting Languages

HTML/XHTML - actually a mark-up language, but more-or-less interpretted line-by-line as a Scripting Language.

Jscript - Microsoft's proprietary variation of JavaScript. MS-IE will run scripts written in conventional JavaScript, but other browsers do not necessarily run scripts written in JScript.

VBScript - a variety of the Visual Basic programming language that will run in MS-IE, but not in most other browsers.

 

Some Server-Side Scripting Languages (just for reference)

CGI/Perl - Perl is a prevalent language for writing scipts that run on the server prior the page being delivered to the user. This allows the user (among other things) to receive a customized page based upon certain criteria. Many of the first CGI (Common Gateway Interface) tools such as guestbooks and page counters were written in Perl.

ASP/JSP/PHP/ColdFusion(CFML) - Several of the popular Server-Side languages in widespread use today. ASP is a Microsoft proprietary langauge for Windows servers runing IIS. ColdFusion requires a purchased Server component, but is available on a variety of platforms. JSP and PHP are included as part of many Web Server products, and are more of an open standard.

 

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