CoffeeScript

CoffeeScript is a web-focused functional and imperative language first appearing in 2009.

Hello World

console.log("Hello World!")

Coding Guide

Language Version

CoffeeScript 2.x (compiled to JavaScript, run on Node.js)

Execution Model

• Source is compiled to JavaScript, then executed by Node.js
• Code runs at the top level
• No explicit main; top-level statements run in order

Key Characteristics

• Significant whitespace (indentation defines blocks)
• No semicolons; newlines and indentation define structure
• Compiles to readable JavaScript
• Case-sensitive

Fragment Authoring

Write valid CoffeeScript: your fragment replaces the template's executable line and can be multiple lines. Use normal indentation for blocks (e.g. 2 spaces). Define functions, loops, and multiple statements as needed.

Available Packages

Node.js built-ins are available: process, fs, path, etc. No extra npm packages are pre-installed.

Common Patterns

• Print: console.log "message"
• Variables: x = 10
• Functions: greet = (name) -> "Hello, #{name}!" or multiline with -> and indented body
• Arrays: [1, 2, 3]
• String interpolation: "Value: #{value}"
• Arguments: process.argv[2..] (first two elements are node and script path)
• Stdin: require('fs').readFileSync(0, 'utf8') or stream with process.stdin

Examples

Simple output

console.log "Hello, World!"

Function and call (multiline)

greet = (name) ->
  "Hello, #{name}!"

console.log greet "Alice"

Loop and aggregation (multiline)

numbers = [1, 2, 3, 4, 5]
squared = (x * x for x in numbers)
sum = squared.reduce (a, b) -> a + b
console.log "Sum of squares: #{sum}"

Reading stdin (multiline)

fs = require 'fs'
input = fs.readFileSync 0, 'utf8'
input.split('\n').forEach (line) ->
  console.log line.toUpperCase()

Command-line args

args = process.argv[2..]
console.log "Args: " + args.join " "

Caveats

• Output with console.log (Node.js API)
• Indentation must be consistent (spaces; typically 2)
• Your fragment can be as many lines as you need

Fraglet Scripts

Coffeescript Fortune

#!/usr/bin/env -S fragletc --vein=coffeescript
console.log "CoffeeScript: where semicolons go to die, and your indentation finally matters."

Echo Args

#!/usr/bin/env -S fragletc --vein=coffeescript
args = process.argv[2..]
console.log "Args: " + args.join " "

Stdin Upper

#!/usr/bin/env -S fragletc --vein=coffeescript
fs = require 'fs'
input = fs.readFileSync 0, 'utf8'
input.split('\n').forEach (line) ->
  console.log line.toUpperCase()

Test

#!/usr/bin/env -S fragletc --vein=coffeescript

console.log("Hello World!")

Connections

Container Info