History[]

Before the second in 2008-2009, the JavaScript engine (also termed JavaScript interpreter or JavaScript implementation) was known as simply an interpreter that read and executed .

The first JavaScript engine was created by at for the web browser. The engine, code named , is implemented in C++. It has since been updated (in JavaScript 1.5) to conform to ECMA-262 Edition 3. The engine, created primarily by Norris Boyd (also at Netscape) is a JavaScript implementation in . Like SpiderMonkey, Rhino is ECMA-262 Edition 3 compliant. Applications of the technology include Apple Safari 4's Nitro, Google Chrome's and Mozilla 's .

By far the most common host environment for JavaScript is a web browser. Web browsers typically use the public (API) to create "host objects" responsible for reflecting the (DOM) into JavaScript.

The is another common application of the engine. A exposes host objects representing an request and response objects, which a JavaScript program then manipulates to dynamically generate web pages. Microsoft's ASP technology for IIS allows server-side code to be written in or JScript (Microsoft's implementation of JavaScript). Jaxer is a web server that runs entirely on JavaScript; this has the benefit of allowing the same code to be shared on the server and on the client.

Performance evolution[]

"..previously behind-the-scenes programming technology called JavaScript is getting new visibility .. "

—-CNET

A typical major browser has a graphical engine and an independent JavaScript engine, which allows for easier testing, reimplementation or use in other projects. For example Carakan is used with Presto; Nitro with WebKit; SpiderMonkey with Gecko; KJS with KHTML; Rhino by default has no layout engine. Other combinations are possible, for example, V8 with WebKit in Google Chrome. The JavaScript engine gives developers access to functionality (networking, DOM handling, external events, HTML5 video, canvas and data storage) needed to control the web browser.

is a for measuring the performance of JavaScript engines in more than a dozen tests, each concentrating on different part of JavaScript language. SunSpider does not use for benchmarking any features beyond those needed to test pure computations (no HTML, no CSS, no networking).

The JavaScript engine race: 2008 and 2009[]

Recently, there has been a race by browser developers to develop even faster JavaScript engines in response to the growing use of JavaScript frameworks and , as the user's experience is directly influenced by the browser's ability to execute the site's client-side code. In 2008, was praised for its JavaScript performance, but other browsers soon received new JavaScript engines which were faster. Later, Chrome won in the races of better performance. Chrome's strength is its application performance and processing speed, both of which were independently verified by multiple websites to be the fastest amongst the major browsers of its time. With the advent of WebKit's and Mozilla's JavaScript virtual machines, Chrome's JavaScript execution performance has been found to be slower. Google responded with the Danish-developed which boosted JavaScript performance in Google Chrome 2.

On June 2, 2008, the WebKit development team announced SquirrelFish, a then-new JavaScript engine that vastly improves Safari's speed at interpreting scripts. The engine was one of the new features in Safari 4, released for developers on June 11, 2008; the final JavaScript engine was called Nitro.

In January 2009, the engine then known as SquirrelFish Extreme (SFX) was enabled for Mac OS X on architectures as it passes all tests on that platform by Apple Inc. Released June 30, 2009, includes the optimization technique that offered "performance improvements ranging between 20 and 40 times faster" compared to in some cases.

The JavaScript engine race: 2010[]

In early 2010, the Norwegian browser replaced the aging Futhark with the faster Carakan, which was 2.5 times faster in early testing. Others in the race, at this time, include Apple's Safari's Nitro (the engine formerly known as SquirrelFish) and Firefox's new JägerMonkey (a "cross-child of Nitro with the older TraceMonkey Engine"). Microsoft lagged behind, lacking a dedicated JavaScript engine and being the slowest of the major browsers. Although by mid-2010, Microsoft held out the carrot of in then unreleased . JägerMonkey began testing in the publicly released beta in Summer 2010., also released in Summer 2010, featured 30 percent faster JavaScript performance than (using the Nitro engine).

2011[]

In 2011, and were released with their JavaScript software.^[]

JavaScript engines[]

Mozilla[]

• , managed by the Mozilla Foundation, open source, developed entirely in Java
• (code name), the first ever JavaScript engine, written by Brendan Eich at Netscape Communications
• , a introduced with
• , the engine introduced with
• , further JIT compiler optimizations for SpiderMonkey, introduced with
• , the engine based on , introduced with
• , by

Google[]

• - open source, developed by Google in Denmark, part of Google Chrome

Opera[]

• , by , used by web browser version 10.50 until switching to with Opera 14 (released in 2013).
• , by Opera Software, used by Opera web browser versions 9.50 to 10.10 until replaced by Carakan in Opera 10.50 (released March 2010).

Safari[]

• - open source, marketed as Nitro and developed by for

Other[]

• - KDE's ECMAScript/JavaScript engine originally developed by for the KDE project's Konqueror web browser
• open source, written by Brendan Eich, who also wrote SpiderMonkey
• , for
• , open source, written by Douglas Campos and others
• , open source as part of OpenJDK, written by Oracle Java Languages and Tool Group
• The open-source JUCE C++ toolkit contains an embedded JavaScript interpreter

Implementations[]

JavaScript is a dialect of , which is supported in many applications, especially . Dialects sometimes include extensions to the language, or to the and related (API) such as the (W3C) specified (DOM). This means that an application written in one dialect may be incompatible with another, unless the applications are written to use only a common subset of supported features and APIs ("core").

A dialect and an implementation are distinct: a dialect of a language is a significant variant of that language, while an implementation of a language (or dialect) executes a program written in that language (or dialect).

Application	Dialect and latest version	ECMAScript edition
, the engine		ECMA-262, edition 5
Mozilla , the layout engine, , and	JavaScript 1.8.5	ECMA-262, edition 5
, the engine		ECMA-262, edition 5.1
	ECMAScript with some JavaScript 1.5 and extensions	ECMA-262, edition 5.1
layout engine, KDE's	JavaScript 1.5	ECMA-262, edition 3
	JavaScript 1.5	ECMA-262, edition 3
	JavaScript 1.4	ECMA-262, edition 3
	JavaScript 1.5	ECMA-262, edition 3
	JavaScript 1.5 with extensions	ECMA-262, edition 3

See also[]

• – Browser speed test

References[]

←

External links[]

• - A daily comparison of bleeding-edge JavaScript engines for Mozilla , and .
• – Browser speed test
• – Online JavaScript speed test
• – Online JavaScript speed test
• – A different open source JavaScript engine on Java platform

[] Dialects engines () Frameworks, libraries () () () () ActionScript Multiple implementations People Other

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