JavaScript is a high-level, dynamic, untyped, and interpreted programming language. It has been standardized in the ECMAScript language specification. Alongside HTML and CSS, it is one of the three essential technologies of World Wide Web content production; the majority of websites employ it and it is supported by all modern web browsers without plug-ins. JavaScript is prototype-based with first-class functions, making it a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles. It has an API for working with text, arrays, dates and regular expressions, but does not include any I/O, such as networking, storage or graphics facilities, relying for these upon the host environment in which it is embedded.
Despite some naming, syntactic, and standard library similarities, JavaScript and Java are otherwise unrelated and have very different semantics. The syntax of JavaScript is actually derived from C, while the semantics and design are influenced by the Self and Scheme programming languages.
History
Beginnings at Netscape
JavaScript was originally developed in 10 days in May 1995 by Brendan Eich, while he was working for Netscape Communications Corporation. Indeed, while competing with Microsoft for user adoption of web technologies and platforms, Netscape considered their client-server offering a distributed OS with a portable version of Sun Microsystems' Java providing an environment in which applets could be run. 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, like Microsoft's Visual Basic (see JavaScript and Java).
Although it was developed under the name Mocha, the language 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. The final choice of name caused confusion, giving the impression that the language was a spin-off of the Java programming language, and the choice has been characterized as a marketing ploy by Netscape to give JavaScript the cachet of what was then the hot new web programming language.
There is a common misconception that the JavaScript language was influenced by an earlier web page scripting language developed by Nombas named C--, not to be confused with the later C-- created in 1997. Brendan Eich, however, had never heard of C-- before he created LiveScript. Nombas did pitch their embedded web page scripting to Netscape, though web page scripting was not a new concept, as shown by ViolaWWW. Nombas later switched to offering JavaScript instead of C-- in their ScriptEase product and was part of the TC39 group that standardized ECMAScript.
Server-side JavaScript
Netscape introduced an implementation of the language for server-side scripting with Netscape Enterprise Server in December, 1995, soon after releasing JavaScript for browsers. Since the mid-2000s, there has been a resurgence of server-side JavaScript implementations, such as Node.js.
Adoption by Microsoft
Microsoft Windows script technologies including VBScript and JScript were released in 1996. JScript, a reverse-engineered implementation of Netscape's JavaScript, was released on July 16, 1996 and was part of Internet Explorer 3, as well as being available server-side in Internet Information Server. IE3 also included Microsoft's first support for Cascading Style Sheets and various extensions to HTML, but in each case the implementation was noticeably different to that found in Netscape Navigator at the time. These differences made it difficult for designers and programmers to make a single website work well in both browsers leading to the use of 'best viewed in Netscape' and 'best viewed in Internet Explorer' logos that characterised these early years of the browser wars. JavaScript began to acquire a reputation for being one of the roadblocks to a cross-platform and standards-driven web. Some developers took on the difficult task of trying to make their sites work in both major browsers, but many could not afford the time. With the release of Internet Explorer 4, Microsoft introduced the concept of Dynamic HTML, but the differences in language implementations and the different and proprietary Document Object Models remained, and were obstacles to widespread take-up of JavaScript on the web.
Standardization
In November 1996, Netscape announced that it had submitted JavaScript to Ecma International for consideration as an industry standard, and subsequent work resulted in the standardized version named ECMAScript. In June 1997, Ecma International published the first edition of the ECMA-262 specification. In June 1998, some modifications were made to adapt it to the ISO/IEC-16262 standard, and the second edition was released. The third edition of ECMA-262 was published on December 1999.
Development of the fourth edition of the ECMAScript standard was never completed. The fifth edition was released in December 2009. The current edition of the ECMAScript standard is 6, released in June 2015.
Later developments
JavaScript has become one of the most popular programming languages on the Web. Initially, however, many professional programmers denigrated the language because its target audience consisted of Web authors and other such "amateurs", among other reasons. The advent of Ajax returned JavaScript to the spotlight and brought more professional programming attention. The result was a proliferation of comprehensive frameworks and libraries, improved JavaScript programming practices, and increased usage of JavaScript outside Web browsers, as seen by the proliferation of server-side JavaScript platforms.
In January 2009, the CommonJS project was founded with the goal of specifying a common standard library mainly for JavaScript development outside the browser.
With the rise of the single-page web app and JavaScript-heavy sites, it is increasingly being used as a compile target for source-to-source compilers from both dynamic languages and static languages. In particular, Emscripten and highly optimized JIT compilers, in tandem with asm.js that is friendly to AOT compilers like OdinMonkey, have enabled C and C++ programs to be compiled into JavaScript and execute at near-native speeds, causing JavaScript to be considered the "assembly language of the web", according to its creator and others.
Trademark
"JavaScript" is a trademark of Oracle Corporation. It is used under license for technology invented and implemented by Netscape Communications and current entities such as the Mozilla Foundation.
