JavaScript is a prototype-based scripting language that is dynamic, weakly typed and has first-class functions. It is a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles.
JavaScript is an interpreted programming or script language from Netscape. It is somewhat similar in capability to Microsoft's Visual Basic, Sun's Tcl, the UNIX-derived Perl, and IBM's REXX. In general, script languages are easier and faster to code in than the more structured and compiled languages such as C and C++. Script languages generally take longer to process than compiled languages, but are very useful for shorter programs.
JavaScript was formalized in the ECMAScript language standard and is primarily used in the form of client-side JavaScript, implemented as part of a web browser in order to create enhanced user interfaces and dynamic websites. This enables programmatic access to computational objects within a host environment. It's most commonly used as part of web browsers, whose implementations allow client-side scripts to interact with the user, control the browser, communicate asynchronously, and alter the document content that is displayed. It is also being used in server-side programming, game development and the creation of desktop and mobile applications.
JavaScript was first developed by Brendan Eich while he was working for Netscape. While the company was battling with Microsoft over the web in the first browser war, Netscape lost. The company then considered their client-server offering a distributed OS, running a portable version of Sun Microsystems' Java. Because Java was a competitor of C++ and aimed at professional programmers, Netscape also wanted a lightweight interpreted language that would complement Java by appealing to nonprofessional programmers.
The scripting language was first developed under the name Mocha, and was officially called LiveScript when it first shipped in beta releases of Netscape Navigator 2.0 in September 1995, but it was renamed JavaScript when it was deployed in the Netscape browser version 2.0B3.
The change of name from LiveScript to JavaScript roughly coincided with Netscape adding support for Java technology in its Netscape Navigator web browser.
JavaScript is used in website development to do such things as:
- Automatically change a formatted date on a web page.
- Cause a linked-to page to appear in a popup window.
- Cause text or a graphic image to change during a mouse rollover.
- Etc..
JavaScript uses some of the same ideas found in Java, the compiled object-oriented programming derived from C++. JavaScript code can be imbedded in HTML pages and interpreted by the web browser (or client). JavaScript can also be run at the server as in Microsoft's Active Server Pages before the page is sent to the requestor. Both Microsoft and Netscape browsers support JavaScript, but sometimes in slightly different ways.
A common misconception is that JavaScript is similar or closely related to Java. It is true that both have a C-like syntax, the C language being their most immediate common ancestor language. They are both object-oriented, typically sandboxed (when used inside a browser), and are widely used in client-side web applications. In addition, JavaScript was designed with Java's syntax and standard library in mind. In particular, all Java keywords were reserved in original JavaScript, JavaScript's standard library follows Java's naming conventions, and JavaScript's Math and Date objects are based on classes from Java 1.0.