jashkenas--coffeescript/documentation/sections/usage.md

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:

Option	Description
-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.
-M, --inline-map	Just like --map, but include the source map directly in the compiled JavaScript files, rather than in a separate file.
-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.
-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
-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]"
-r, --require [MODULE]	require() the given module before starting the REPL or evaluating the code given with the --eval flag.
-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. Used for debugging the compiler.
-n, --nodes	Instead of compiling the CoffeeScript, just lex and parse it, and print out the parse tree. Used for debugging the compiler.
--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.
--no-header	Suppress the “Generated by CoffeeScript” header.

Examples:

• Compile a directory tree of .coffee files in src into a parallel tree of .js files in lib:
  coffee --compile --output lib/ src/
• Watch a file for changes, and recompile it every time the file is saved:
  coffee --watch --compile experimental.coffee
• Concatenate a list of files into a single script:
  coffee --join project.js --compile src/*.coffee
• Print out the compiled JS from a one-liner:
  coffee -bpe "alert i for i in [0..10]"
• All together now, watch and recompile an entire project as you work on it:
  coffee -o lib/ -cw src/
• Start the CoffeeScript REPL (Ctrl-D to exit, Ctrl-Vfor multi-line):
  coffee

ES2015+ Output

CoffeeScript 2 outputs the latest ES2015+ syntax. If you’re looking for a single tool that takes CoffeeScript input and generates JavaScript output that runs in any JavaScript runtime, assuming you opt out of certain newer features, stick to CoffeeScript 1.x. CoffeeScript 2 breaks compatibility with certain CoffeeScript 1.x features in order to conform with the ES2015+ specifications, and generate more idiomatic output (a CoffeeScript => becomes an ES =>; a CoffeeScript class becomes an ES class; and so on).

Since the CoffeeScript 2 compiler outputs ES2015+ syntax, it is your responsibility to either ensure that your target JavaScript runtime(s) support all these features, or that you pass the output through another transpiler like Babel, Rollup or Traceur Compiler. In general, CoffeeScript 2’s output is supported as is by Node.js 7.6+, except for modules and JSX which require transpilation.

There are many great task runners for setting up JavaScript build chains, such as Gulp, Webpack, Grunt and Broccoli. If you’re looking for a very minimal solution to get started, you can use babel-preset-env and the command line:

npm install --global coffeescript@next
npm install --save-dev coffeescript@next babel-cli babel-preset-env
coffee --print *.coffee | babel --presets env > app.js

Node.js

If you’d like to use Node.js’ CommonJS to require CoffeeScript files, e.g. require './app.coffee', you must first “register” CoffeeScript as an extension:

require 'coffeescript/register'

App = require './app' # The .coffee extension is optional

If you want to use the compiler’s API, for example to make an app that compiles strings of CoffeeScript on the fly, you can require the full module:

CoffeeScript = require 'coffeescript'

eval CoffeeScript.compile 'console.log "Mmmmm, I could really go for some #{Math.pi}"'

The compile method has the signature compile(code, options) where code is a string of CoffeeScript code, and the optional options is an object with some or all of the following properties:

• options.sourceMap, boolean: if true, a source map will be generated; and instead of returning a string, compile will return an object of the form {js, v3SourceMap, sourceMap}.
• options.inlineMap, boolean: if true, output the source map as a base64-encoded string in a comment at the bottom.
• options.filename, string: the filename to use for the source map.
• options.bare, boolean: if true, output without the top-level function safety wrapper.
• options.header, boolean: if true, output the Generated by CoffeeScript header.