CoffeeScript 是逐句编译为 JavaScript 的一种小型语言，且没有运行时的解释器。 作为JavaScrip t的替代品之一，CoffeeScript 旨在编译人类可读、美观优雅且速度不输原生的代码， 且编译后的代码可以在任何 JavaScript 运行时正确运行。

参阅 CoffeeScript 官方网站以获取 CoffeeScript的完整教程。

CoffeeScript 是一种很潮的编程语言，它紧随众多现代编程语言的趋势。 因此正如 Ruby 和 Python，CoffeeScript 使用井号标记注释。

# 这是注释

###
大段落注释以此为例，可以被直接编译为 '/ *' 和 '* /' 包裹的JavaScript代码。

在继续之前你需要了解JavaScript的基本概念。

示例中 => 后为编译后的JavaScript代码
###

赋值

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

条件

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

函数

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 + "...";
#};

区间

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

对象

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);
#};

存在判断

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

数组推导

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);
#  }
#}