Rhino

Implementation of programming language ECMAScript

Rhino is another JavaScript engine. It is open-source and is managed by Mozilla Foundation.

Rhino is written in Java; it converts JavaScript code into Java classes, and can work both in compiler and interpreter mode.

Examples:

Hello, World!:

Example for versions Rhino 1.6, SpiderMonkey 1.7

JavaScript uses different commands to output messages depending on what environment is it used in:

  • print: for interpreters with command-line interface prints the message to standard output stream, but when used in web-browser, calls print dialog instead;
  • document.write: when used in web-browser, prints the message to the current document (web-page);
  • console.log: a command for Firebug plugin which prints the message to debug console of the plugin;
  • alert: when used in web-browser, creates a pop-up information window with the message.

Note that three last commands won’t work in non-browser-based environment, since they use objects (document and console) which are not defined in command-line interfaces.

The example itself works in a smart universal way: since it can be executed in multiple environments with various objects defined, it checks each object in turn, and uses the first available writing method. 

if (typeof console === 'object') {
    console.log('Hello, World!');
} else if (typeof document === 'object') {
    document.write('Hello, World!');
} else {
    print('Hello, World!');
}