JavaScript, programming language of the Web, is used primarily on websites and web applications and executed by web browsers. However JavaScript is general purpose language and can be used for other programming tasks. It can be used on server side, what in this case means every place outside of the web browser.
JavaScript engines
There are several implementations of JavaScript, that are JavaScript engines. JavaScript engines interpret and execute JavaScript code. They are used commonly in web browsers but can also be used in other host environments like web server.
JavaScript engines expose a public API which can be used to integrate JavaScript into other software and embed in other environment (like web browser, web server, database).
SpiderMonkey – the first JavaScript engine created by Brendan Eich, creator of JavaScript and maintenanced by Mozilla Foundation. Implemented in C/C++.
Initially build for Netscape Navigator, currently powers Mozilla Firefox.
Rhino is another JavaScript engine maintenanced by Mozilla Foundation. It is written in Java. Rhino gives JavaScript access to Java API. JavaScript can call Java methods, set Java properties, convert JavaScript values to Java values and vice versa.
Chrome V8 – JavaScript framework maintenanced by Google for their Chrome browser. It is written in C++.
JScript & Chacra – engines developed by Microsoft for their web browsers Internet Explorer and Edge.
JavaScriptCore (Nitro) – engine developed by Apple for Safari.
Runtime Environment
JavaScript Runtime Environment is a container in which works JavaScript engine and runs scripts. JavaScript is embedded language and uses additional libraries which depend on the context. Runtime Environment provides these additional objects and functions. For example, the window and the document are additional objects in the web browser.
Server-side JavaScript use
Below are some examples of using JavaScript on server side:
MongoDB – document oriented database, uses SpiderMonkey engine.
CouchDB – noSQL database, uses SpiderMonkey engine.
Riak – distributed, noSQL key-value database, uses SpiderMonkey engine.
Thunderbird – email client, uses SpiderMonkey engine.
Adobe Acrobat, Reader, Flash – use SpiderMonkey engine.
GNOME – desktop environment for UNIX-like operating systems, uses SpiderMonkey engine.
Rhino uses Java API and allows you to convert JavaScript scripts into Java classes. Using Rhino shell you can run scripts in batch mode.
Node.js is a JavaScript runtime environment that allows you to execute JavaScript code on server side. It is build on V8 engine. Node.js is used to build scalable network applications. It is based on asynchronous, event driven communication, that allows you to handle high loads effectively.
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