CoffeeScript

CoffeeScript is a little language that compiles into JavaScript.
CoffeeScript is an attempt to expose the good parts of JavaScript in a simple way.
The golden rule of CoffeeScript is: "It's just JavaScript". The code compiles one-to-one into the equivalent JS, and there is no interpretation at runtime. You can use any existing JavaScript library seamlessly from CoffeeScript (and vice-versa). The compiled output is readable and pretty-printed, will work in every JavaScript runtime, and tends to run as fast or faster than the equivalent handwritten JavaScript.
 CoffeeScript is a lucid evolution of JavaScript created by Jeremy Ashkenas. CoffeeScript is available in browsers and environments where JavaScript

is available

Installation

The CoffeeScript compiler is itself written in CoffeeScript, using the Jison parser generator. The command-line version of coffee is available as a Node.js utility. The core compiler however, does not depend on Node, and can be run in any JavaScript environment, or in the browser.

Usage

Once installed, you should have access to the coffee command, which can execute scripts, compile .coffee files into .js, and provide an interactive REPL. The coffee command takes the following options: 

-c, --compile Compile a .coffee script into a .js JavaScript file of the same name. -m, --map Generate source maps alongside the compiled JavaScript files. Adds sourceMappingURL directives to the JavaScript as well. -i, --interactive Launch an interactive CoffeeScript session to try short snippets. Identical to calling coffee with no arguments. -o, --output [DIR] Write out all compiled JavaScript files into the specified directory. Use in conjunction with --compile or --watch. -j, --join [FILE] Before compiling, concatenate all scripts together in the order they were passed, and write them into the specified file. Useful for building large projects. -w, --watch Watch files for changes, rerunning the specified command when any file is updated. -p, --print Instead of writing out the JavaScript as a file, print it directly to stdout. -s, --stdio Pipe in CoffeeScript to STDIN and get back JavaScript over STDOUT. Good for use with processes written in other languages. An example: cat src/cake.coffee | coffee -sc -l, --literate Parses the code as Literate CoffeeScript. You only need to specify this when passing in code directly over stdio, or using some sort of extension-less file name. -e, --eval Compile and print a little snippet of CoffeeScript directly from the command line. For example: coffee -e "console.log num for num in [10..1]" -b, --bare Compile the JavaScript without the top-level function safety wrapper. -t, --tokens Instead of parsing the CoffeeScript, just lex it, and print out the token stream: [IDENTIFIER square] [ASSIGN =] [PARAM_START (] ... -n, --nodes Instead of compiling the CoffeeScript, just lex and parse it, and print out the parse tree: Expressions   Assign     Value "square"     Code "x"       Op *         Value "x"         Value "x" --nodejs The node executable has some useful options you can set, such as --debug, --debug-brk, --max-stack-size, and --expose-gc. Use this flag to forward options directly to Node.js. To pass multiple flags, use --nodejs multiple times.