Coffeescript

Install

npm install -g coffee-script

Compile to JS

// watch & recompile an entire project as you work

coffee -o lib/ -cw src

## Join Files

Compile .coffee files to a single .js file.

coffee -j js/app.js -c src/*.coffee

Syntax

Assignment

Coffeescript:

# Assignment:
number   = 42
opposite = true

JS:

var number, opposite;

number = 42;
opposite = true;

Conditions

Coffeescript:

number = -42 if opposite

JS:

var number;

if (opposite) {
  number = -42;
}

Functions

Coffeescript:

square = (x) -> x * x
var square;

square = function(x) {
  return x * x;
};

Arrays

Coffeescript:

# Arrays:
list = [1, 2, 3, 4, 5]
var list;
list = [1, 2, 3, 4, 5];

Objects

Coffeescript:

# Objects:
math =
  root:   Math.sqrt
  square: square
  cube:   (x) -> x * square x

JS:

var math;

math = {
  root: Math.sqrt,
  square: square,
  cube: function(x) {
    return x * square(x);
  }
};

Splats

Coffeescript:

race = (winner, runners...) ->
  print winner, runners

JS:

var race,
  slice = [].slice;

race = function() {
  var runners, winner;
  winner = arguments[0], runners = 2 <= arguments.length ? slice.call(arguments, 1) : [];
  return print(winner, runners);
};

Existence

Coffeescript:

# Existence:
console.log "I knew it!" if elvis?

JS:

if (typeof elvis !== "undefined" && elvis !== null) {
  console.log("I knew it!");
}

Array Comprehensions

Coffeescript:

# Array comprehensions:
cubes = (math.cube num for num in list)
var cubes, num;

cubes = (function() {
  var i, len, results;
  results = [];
  for (i = 0, len = list.length; i < len; i++) {
    num = list[i];
    results.push(math.cube(num));
  }
  return results;
})();

Reference

http://coffeescript.org/