What javascript engine is needed?

A JavaScript engine is a software component that executes JavaScript code. The first JavaScript engines were mere interpreters, but all relevant modern engines use just-in-time compilation for improved performance.[1]

JavaScript engines are typically developed by web browser vendors, and every major browser has one. In a browser, the JavaScript engine runs in concert with the rendering engine via the Document Object Model.

The use of JavaScript engines is not limited to browsers. For example, the V8 engine is a core component of the Node.js and Deno runtime systems.

Since ECMAScript is the standardized specification of JavaScript, ECMAScript engine is another name for these engines. With the advent of WebAssembly, some engines can also execute this code in the same sandbox as regular JavaScript code.

History[edit]

The first JavaScript engine was created by Brendan Eich in 1995 for the Netscape Navigator web browser. It was a rudimentary interpreter for the nascent language Eich invented. (This evolved into the SpiderMonkey engine, still used by the Firefox browser.)

The first modern JavaScript engine was V8, created by Google for its Chrome browser. V8 debuted as part of Chrome in 2008, and its performance was much better than any prior engine.[2][3] The key innovation was just-in-time compilation, which can significantly improve execution times.

Other browser vendors needed to overhaul their interpreters to compete.[4] Apple developed the Nitro engine for its Safari browser, which had 30% better performance than its predecessor.[5] Mozilla leveraged portions of Nitro to improve its own SpiderMonkey engine.[6]

Since 2017, these engines have added support for WebAssembly. This enables the use of pre-compiled executables for performance-critical portions of page scripts.

Notable engines[edit]

• V8 from Google is the most used JavaScript engine. Google Chrome and the many other Chromium-based browsers use it, as do applications built with CEF, Electron, or any other framework that embeds Chromium. Other uses include the Node.js and Deno runtime systems.
• SpiderMonkey is developed by Mozilla for use in Firefox and its forks. The GNOME Shell uses it for extension support.
• JavaScriptCore is Apple's engine for its Safari browser. Other WebKit-based browsers also use it. KJS from KDE was the starting point for its development.[7]
• Chakra is the engine of the Internet Explorer browser. It was also forked by Microsoft for the original Edge browser, but Edge was later rebuilt as a Chromium-based browser and thus now uses V8.[8][9]

• The James Webb Space Telescope Integrated Science Instrument Module reportedly embeds a standalone JavaScript engine that runs JS code.[10]

References[edit]

1. ^ Looper, Jen (2015-09-21). "A Guide to JavaScript Engines for Idiots". Telerik Developer Network. Archived from the original on 2018-12-08. Retrieved 2018-12-08.
2. ^ "Big browser comparison test: Internet Explorer vs. Firefox, Opera, Safari and Chrome". PC Games Hardware. Computec Media AG. Retrieved 2010-06-28.
3. ^ "Lifehacker Speed Tests: Safari 4, Chrome 2". Lifehacker. Retrieved 2010-06-28.
4. ^ "Mozilla asks, 'Are we fast yet?'". Wired. Retrieved 18 January 2019.
5. ^ Safari 5 Released
6. ^ Shankland, Stephen (2010-03-02). "Opera 10.5 brings new JavaScript engine". CNET. CBS Interactive. Retrieved 2012-01-30.
7. ^ Stachowiak, Maciej (November 9, 2008). "Companies and Organizations that have contributed to WebKit". WebKit Wiki. Retrieved April 13, 2019.
8. ^ Belfiore, Joe (2020-01-15), New year, new browser – The new Microsoft Edge is out of preview and now available for download, Microsoft
9. ^ "Microsoft Edge and Chromium Open Source: Our Intent". Microsoft Edge Team. 6 December 2018. Retrieved 8 December 2018.
10. ^ Clark, Mitchell (2022-08-18). "The James Webb Space Telescope runs JavaScript, apparently". The Verge. Retrieved 2022-09-02.

JavaScript is not understandable by computer but the only browser understands JavaScript. So, we need a program to convert our JavaScript program into computer-understandable language. A JavaScript engine is a computer program that executes JavaScript code and converts it into computer understandable language.

List of JavaScript Engines:

Let’s understand each of them.

1. V8: V8 is a JavaScript engine developed by the Chromium Project for Google Chrome and Chromium web browsers. It is a JavaScript engine that can run standalone, or be embedded into any C++ application. Using its own parser, it generates an abstract syntax tree. Then, Ignition generates bytecode from this syntax tree using the internal V8 bytecode format. Bytecode is compiled into machine code by TurboFan. It also handles memory allocation for objects, and garbage collects objects it no longer needs. Optimization techniques such as elision of expensive runtime properties, and inline caching. The garbage collector is a generational incremental collector.

V8 provides an edge as it allows JavaScript to run much faster, which improves users’ experience of the web, paves the way for the development of web applications, and spurs rapid growth of server-side JavaScript through projects like Node.js.

2. Chakra: Chakra is a JScript engine developed by Microsoft. It is proprietary software. It is used in the Internet Explorer web browser. A distinctive feature of the engine is that it JIT compiles scripts on a separate CPU core, parallel to the web browser.

3. Spider Monkey: SpiderMonkey is the first JavaScript engine, written by Brendan Eich at Netscape Communications, later released as open-source and currently maintained by the Mozilla Foundation. It is still used in the Firefox web browser.

4. Webkit: WebKit is developed by Apple and  used in its Safari web browser, as well as all iOS web browsers. It is  used by the BlackBerry Browser, PlayStation consoles beginning from the PS3, the Tizen mobile operating systems, and a browser included with the Amazon Kindle e-book reader. WebKit’s C++ application programming interface (API) provides a set of classes to display Web content in windows and implements browser features such as following links when clicked by the user, managing a back-forward list, and managing a history of pages recently visited.

Example 1: Executing JavaScript code by using console: For Nashorn engine, Java 8 introduced one new command-line tool i.e.jjl. We have to follow the below steps to execute JavaScript code through the console:

• Create a file named with geeksforgeeks.js.
• Open geeks.js and write following code into the file and save it.

Javascript