learnxinyminutes-docs/coffeescript.html.markdown

language	contributors	filename
coffeescript	Tenor Biel http://github.com/L8D Xavier Yao http://github.com/xavieryao	coffeescript.coffee

CoffeeScript is a little language that compiles one-to-one into the equivalent JavaScript, and there is no interpretation at runtime. As one of the successors to JavaScript, CoffeeScript tries its best to output readable, pretty-printed and smooth-running JavaScript code, which works well in every JavaScript runtime. It also attempts to try and make JavaScript more in line with the trends of many modern languages.

See also the CoffeeScript website, which has a complete tutorial on CoffeeScript.

# Comments are similar to Ruby and Python, using the hash symbol `#`

###
Block comments are like these, and they translate directly to '/ *'s and '* /'s
for the resulting JavaScript code.

You should understand most of JavaScript semantics
before continuing.
###

# Assignment:
number   = 42 #=> var number = 42;
opposite = true #=> var opposite = true;

# Conditions:
number = -42 if opposite #=> if(opposite) { number = -42; }

# Functions:
square = (x) -> x * x #=> var square = function(x) { return x * x; }

fill = (container, liquid = "coffee") ->
  "Filling the #{container} with #{liquid}..."
#=>var fill;
#
#fill = function(container, liquid) {
#  if (liquid == null) {
#    liquid = "coffee";
#  }
#  return "Filling the " + container + " with " + liquid + "...";
#};

# Ranges:
list = [1..5] #=> var list = [1, 2, 3, 4, 5];

# Objects:
math =
  root:   Math.sqrt
  square: square
  cube:   (x) -> x * square x
#=> var math = {
#    "root": Math.sqrt,
#    "square": square,
#    "cube": function(x) { return x * square(x); }
#   };

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

# Existence:
alert "I knew it!" if elvis?
#=> if(typeof elvis !== "undefined" && elvis !== null) { alert("I knew it!"); }

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

foods = ['broccoli', 'spinach', 'chocolate']
eat food for food in foods when food isnt 'chocolate'
#=>foods = ['broccoli', 'spinach', 'chocolate'];
#
#for (_k = 0, _len2 = foods.length; _k < _len2; _k++) {
#  food = foods[_k];
#  if (food !== 'chocolate') {
#    eat(food);
#  }
#}

Additional resources

• Smooth CoffeeScript
• CoffeeScript Ristretto