CoffeeScript

CoffeeScript 是一门编译到 JavaScript 的小巧语言. 在 Java 般笨拙的外表下, JavaScript 其实有着一颗华丽的心脏. CoffeeScript 尝试用简洁的方式展示 JavaScript 优秀的部分.

CoffeeScript 的指导原则是: "她仅仅是 JavaScript". 代码一一对应地编译到 JS, 不会在编译过程中进行解释. 已有的 JavaScript 类库可以无缝地和 CoffeeScript 搭配使用, 反之亦然. 编译后的代码是可读的, 且经过美化, 能在所有 JavaScript 环境中运行, 并且应该和对应手写的 JavaScript 一样快或者更快.

最新版本: 1.7.1

sudo npm install -g coffee-script

概览

左边是 CoffeeScript, 右边是编译后输出的 JavaScript.

# 赋值:number   = 42opposite = true# 条件:number = -42 if opposite# 函数:square = (x) -> x * x# 数组:list = [1, 2, 3, 4, 5]# 对象:math =  root:   Math.sqrt  square: square  cube:   (x) -> x * square x# Splats:race = (winner, runners...) ->
  print winner, runners# 存在性:alert "I knew it!" if elvis?# 数组 推导(comprehensions):cubes = (math.cube num for num in list)

var cubes, list, math, num, number, opposite, race, square,
  __slice = [].slice;

number = 42;

opposite = true;if (opposite) {
  number = -42;
}

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

list = [1, 2, 3, 4, 5];

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

race = function() {
  var runners, winner;
  winner = arguments[0], runners = 2 <= arguments.length ? __slice.call(arguments, 1) : [];  return print(winner, runners);
};if (typeof elvis !== "undefined" && elvis !== null) {
  alert("I knew it!");
}

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;
})();

run: cubes

安装

CoffeeScript 编译器本身是 CoffeeScript 写的, 使用了 Jison parser generator. 命令行版本的 coffee 是一个实用的 Node.js 工具. 不过编译器并不依赖 Node, 而是能运行于任何 JavaScript 执行环境, 比如说在浏览器里(看上边的"试一试 CoffeeScript").

安装前你需要最新稳定版 Node.js, 和 npm (Node Package Manager). 借助 npm 可以安装 CoffeeScript:

npm install -g coffee-script

(如果不想全局安装可以去掉 -g 选项.)

如果你希望安装 master 分支上最新的 CoffeeScript, 你可以从源码仓库 克隆 CoffeeScript, 或直接下载源码. 还有通过 npm 方式安装 master 分支最新的 CoffeeScript 编译器:

npm install -g http://github.com/jashkenas/coffee-script/tarball/master

或者你想将其安装到 /usr/local, 而不用 npm 进行管理, 进入 coffee-script 目录执行:

sudo bin/cake install

用法

安装之后, 你应该可以运行 coffee 命令以执行脚本, 编译 .coffee 文件到 .js 文件, 和提供一个交互式的 REPL. coffee 命令有下列参数:

-c, --compile	编译一个 .coffee 脚本到一个同名的 .js 文件.
-m, --map	随 JavaScript 文件一起生成 source maps. 并且在 JavaScript 里加上 sourceMappingURL 指令.
-i, --interactive	启动一个交互式的 CoffeeScript 会话用来尝试一些代码片段. 等同于执行 coffee 而不加参数.
-o, --output [DIR]	将所有编译后的 JavaScript 文件写到指定文件夹. 与 --compile 或 --watch 搭配使用.
-j, --join [FILE]	编译之前, 按参数传入顺序连接所有脚本到一起, 编译后写到指定的文件. 对于编译大型项目有用.
-w, --watch	监视文件改变, 任何文件更新时重新执行命令.
-p, --print	JavaScript 直接打印到 stdout 而不是写到一个文件.
-s, --stdio	将 CoffeeScript 传递到 STDIN 后从 STDOUT 获取 JavaScript. 对其他语言写的进程有好处. 比如: cat src/cake.coffee | coffee -sc
-l, --literate	将代码作为 Literate CoffeeScript 解析. 只会在从 stdio 直接传入代码或者处理某些没有后缀的文件名需要写明这点.
-e, --eval	直接从命令行编译和打印一小段 CoffeeScript. 比如: coffee -e "console.log num for num in [10..1]"
-b, --bare	编译到 JavaScript 时去掉顶层函数的包裹.
-t, --tokens	不对 CoffeeScript 进行解析, 仅仅进行 lex, 打印出 token stream: [IDENTIFIER square] [ASSIGN =] [PARAM_START (] ...
-n, --nodes	不对 CoffeeScript 进行编译, 仅仅 lex 和解析, 打印 parse tree: Expressions   Assign     Value "square"     Code "x"       Op *         Value "x"         Value "x"
--nodejs	node 命令有一些实用的参数, 比如 --debug, --debug-brk, --max-stack-size, 和 --expose-gc. 用这个参数直接把参数转发到 Node.js. 重复使用 --nodejs 来传递多个参数.

例子:

• 编译一个 .coffee 文件的树形目录 src 到一个同级 .js 文件树形目录 lib:
  coffee --compile --output lib/ src/

• 监视一个文件的改变, 每次文件被保证时重新编译:
  coffee --watch --compile experimental.coffee

• 合并一组文件到单个脚本:
  coffee --join project.js --compile src/*.coffee

• 从一个 one-liner 打印编译后的 JS:
  coffee -bpe "alert i for i in [0..10]"

• 现在全部一起, 在你工作时监视和重复编译整个项目:
  coffee -o lib/ -cw src/

• 运行 CoffeeScript REPL (Ctrl-D 来终止, Ctrl-V 激活多行):
  coffee

Literate CoffeeScript

除了被作为一个普通的编程语言, CoffeeScript 也可以在 "literate" 模式下编写。 如果你以 .litcoffee 为扩展名命名你的文件, 你可以把它当作 Markdown 文件来编写 — 此文档恰好也是一份可执行的 CoffeeScript 代码, 编译器将会把所有的缩进块 (Markdown 表示源代码的方式) 视为代码, 其他部分则为注释.

Just for kicks, a little bit of the compiler is currently implemented in this fashion: See it as a document, raw, and properly highlighted in a text editor.

I'm fairly excited about this direction for the language, and am looking forward to writing (and more importantly, reading) more programs in this style. More information about Literate CoffeeScript, including an example program, are available in this blog post.

语言手册

这份手册所设计的结构, 方便从上往下进行阅读. 后边的章节使用前面介绍的语法和手法. 阅读这份手册需要对 JavaScript 比较熟悉. 以下所有的例子, CoffeeScript 源码将在左边显示, 并在右侧直接编译到 JavaScript.

很多例子可以通过点击右边的 run 按钮直接运行(代码有意义的话), 也可以通过点击左边的 load 按钮载入"试一试 CoffeeScript"的控制台.

首先, 一些基础, CoffeeScript 使用显式的空白来区分代码块. 你不需要使用分号 ; 来关闭表达式, 在一行的结尾换行就可以了(尽管分号依然可以用来把多行的表达式简写到一行里). 不需要再用花括号来 { } 包裹代码快, 在 函数, if 表达式, switch, 和 try/catch 当中使用缩进.

传入参数的时候, 你不需要再使用圆括号来表明函数被执行. 隐式的函数调用的作用范围一直到行尾或者一个块级表达式.
console.log sys.inspect object → console.log(sys.inspect(object));

函数 函数通过一组可选的圆括号包裹的参数, 一个箭头, 一个函数体来定义. 一个空的函数像是这样: ->

square = (x) -> x * xcube   = (x) -> square(x) * x

var cube, square;

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

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

load

run: cube(5)

一些函数函数参数会有默认值, 当传入的参数的不存在 (null 或者 undefined) 时会被使用.

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 + "...";
};

load

run: fill("cup")

对象和数组 CoffeeScript 中对象和数组的字面量看起来很像在 JavaScript 中的写法. 如果单个属性被写在自己的一行里, 那么逗号是可以省略的. 和 YAML 类似, 对象可以用缩进替代花括号来声明.

song = ["do", "re", "mi", "fa", "so"]

singers = {Jagger: "Rock", Elvis: "Roll"}

bitlist = [  1, 0, 1
  0, 0, 1
  1, 1, 0]

kids =  brother:    name: "Max"
    age:  11
  sister:    name: "Ida"
    age:  9

var bitlist, kids, singers, song;

song = ["do", "re", "mi", "fa", "so"];

singers = {
  Jagger: "Rock",
  Elvis: "Roll"};

bitlist = [1, 0, 1, 0, 0, 1, 1, 1, 0];

kids = {
  brother: {
    name: "Max",
    age: 11
  },
  sister: {
    name: "Ida",
    age: 9
  }
};

load

run: song.join(" ... ")

JavaScript 里, 你不能使用不添加引号的保留字段作为属性名称, 比如 class. CoffeeScript 里作为键出现的保留字会被识别并补上引号, 所以你不用有额外的操心(比如说, 使用 jQuery 的时候).

$('.account').attr class: 'active'

log object.class

$('.account').attr({  "class": 'active'});

log(object["class"]);

load

词法作用域和变量安全 CoffeeScript 编译器会考虑所有变量, 保证每个变量都在词法域里适当地被定义 — 你永远不需要自己去写 var.

outer = 1changeNumbers = ->
  inner = -1
  outer = 10inner = changeNumbers()

var changeNumbers, inner, outer;

outer = 1;

changeNumbers = function() {
  var inner;
  inner = -1;  return outer = 10;
};

inner = changeNumbers();

load

run: inner

注意所有变量的定义都被推到相关的顶层作用域, 也就是第一次出现的位置. outer 在内层的函数里没有被重新定义, 因为它已经存在于作用域当中了. 同时, 内层函数里的 inner 不应该改变外部的同名的变量, 所以在这里有自己的声明.

其行为和 Ruby 的局部变量的作用域实际上是一致的. 由于你没有对 var 关键字的直接访问, 根据需要隐藏一个外部变量就很容易, 你只能引用它. 所以在写深层的嵌套的函数时, 注意不要意外用到和外部变量相同的名字.

尽管要说清楚会受到文档长度限制, 函数的所有 CoffeeScript 结果都被一个匿名函数包裹: (function(){ ... })(); 这层安全的封装, 加上自动生成的 var 关键字, 使得不小心污染全局命名空间很难发生.

如果你希望创建一个其他脚本也能使用的顶层变量, 那么将其作为赋值在 window 上, 或者在 CommonJS 里的 exports 上. 存在操作符(existential operator)可以帮你写出一个可靠的方式找到添加位置; 比如你的目标是同时满足 CommonJS 和浏览器: exports ? this

if, else, unless 和条件赋值 if/else 表达式可以不用圆括号和花括号就写出来. 就像函数和其他块级表达式那样, 多行的条件可以通过缩进来表明. 另外还有一个顺手的后缀形式, 在行尾使用 if or unless.

CoffeeScript 会尝试编译 if 语句到 JavaScript 表达式, 或者一个封装的闭包. CoffeeScript 里不存在直白的三元表达式. — 你只要在一行内使用普通的 if 语句.

mood = greatlyImproved if singingif happy and knowsIt
  clapsHands()
  chaChaCha()else
  showIt()

date = if friday then sue else jill

var date, mood;if (singing) {
  mood = greatlyImproved;
}if (happy && knowsIt) {
  clapsHands();
  chaChaCha();
} else {
  showIt();
}

date = friday ? sue : jill;

load

变参(splats)... 使用 JavaScript 的 arguments 对象是一种处理接收不定数量个参数的函数常用办法. CoffeeScript 在函数定义和调用里提供了变参(splats) ... 的语法, 让不定个数的参数使用起来更愉悦一些.

gold = silver = rest = "unknown"awardMedals = (first, second, others...) ->
  gold   = first
  silver = second
  rest   = others

contenders = [  "Michael Phelps"
  "Liu Xiang"
  "Yao Ming"
  "Allyson Felix"
  "Shawn Johnson"
  "Roman Sebrle"
  "Guo Jingjing"
  "Tyson Gay"
  "Asafa Powell"
  "Usain Bolt"]

awardMedals contenders...

alert "Gold: " + gold
alert "Silver: " + silver
alert "The Field: " + rest

var awardMedals, contenders, gold, rest, silver,
  __slice = [].slice;

gold = silver = rest = "unknown";

awardMedals = function() {
  var first, others, second;
  first = arguments[0], second = arguments[1], others = 3 <= arguments.length ? __slice.call(arguments, 2) : [];
  gold = first;
  silver = second;  return rest = others;
};

contenders = ["Michael Phelps", "Liu Xiang", "Yao Ming", "Allyson Felix", "Shawn Johnson", "Roman Sebrle", "Guo Jingjing", "Tyson Gay", "Asafa Powell", "Usain Bolt"];

awardMedals.apply(null, contenders);

alert("Gold: " + gold);

alert("Silver: " + silver);

alert("The Field: " + rest);

load

run

Loops and Comprehensions Most of the loops you'll write in CoffeeScript will be comprehensions over arrays, objects, and ranges. Comprehensions replace (and compile into) for loops, with optional guard clauses and the value of the current array index. Unlike for loops, array comprehensions are expressions, and can be returned and assigned.

# 吃午饭.eat food for food in ['toast', 'cheese', 'wine']# 精致的五道菜.courses = ['greens', 'caviar', 'truffles', 'roast', 'cake']
menu i + 1, dish for dish, i in courses# 注重健康的一餐.foods = ['broccoli', 'spinach', 'chocolate']
eat food for food in foods when food isnt 'chocolate'

var courses, dish, food, foods, i, _i, _j, _k, _len, _len1, _len2, _ref;

_ref = ['toast', 'cheese', 'wine'];for (_i = 0, _len = _ref.length; _i < _len; _i++) {
  food = _ref[_i];
  eat(food);
}

courses = ['greens', 'caviar', 'truffles', 'roast', 'cake'];for (i = _j = 0, _len1 = courses.length; _j < _len1; i = ++_j) {
  dish = courses[i];
  menu(i + 1, dish);
}

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

load

Comprehensions should be able to handle most places where you otherwise would use a loop, each/forEach, map, or select/filter, for example: shortNames = (name for name in list when name.length < 5)
If you know the start and end of your loop, or would like to step through in fixed-size increments, you can use a range to specify the start and end of your comprehension.

countdown = (num for num in [10..1])

var countdown, num;

countdown = (function() {
  var _i, _results;
  _results = [];  for (num = _i = 10; _i >= 1; num = --_i) {
    _results.push(num);
  }  return _results;
})();

load

run: countdown

Note how because we are assigning the value of the comprehensions to a variable in the example above, CoffeeScript is collecting the result of each iteration into an array. Sometimes functions end with loops that are intended to run only for their side-effects. Be careful that you're not accidentally returning the results of the comprehension in these cases, by adding a meaningful return value — like true — or null, to the bottom of your function.

To step through a range comprehension in fixed-size chunks, use by, for example:
evens = (x for x in [0..10] by 2)

Comprehensions can also be used to iterate over the keys and values in an object. Use of to signal comprehension over the properties of an object instead of the values in an array.

yearsOld = max: 10, ida: 9, tim: 11ages = for child, age of yearsOld  "#{child} is #{age}"

var age, ages, child, yearsOld;

yearsOld = {
  max: 10,
  ida: 9,
  tim: 11};

ages = (function() {
  var _results;
  _results = [];  for (child in yearsOld) {
    age = yearsOld[child];
    _results.push("" + child + " is " + age);
  }  return _results;
})();

load

run: ages.join(", ")

If you would like to iterate over just the keys that are defined on the object itself, by adding a hasOwnProperty check to avoid properties that may be inherited from the prototype, use
for own key, value of object

The only low-level loop that CoffeeScript provides is the while loop. The main difference from JavaScript is that the while loop can be used as an expression, returning an array containing the result of each iteration through the loop.

# 经济 101if this.studyingEconomics
  buy()  while supply > demand
  sell() until supply > demand# 摇篮曲num = 6lyrics = while num -= 1
  "#{num} little monkeys, jumping on the bed.
    One fell out and bumped his head."

var lyrics, num;if (this.studyingEconomics) {  while (supply > demand) {
    buy();
  }  while (!(supply > demand)) {
    sell();
  }
}

num = 6;

lyrics = (function() {
  var _results;
  _results = [];  while (num -= 1) {
    _results.push("" + num + " little monkeys, jumping on the bed. One fell out and bumped his head.");
  }  return _results;
})();

load

run: lyrics.join(" ")

For readability, the until keyword is equivalent to while not, and the loop keyword is equivalent to while true.

When using a JavaScript loop to generate functions, it's common to insert a closure wrapper in order to ensure that loop variables are closed over, and all the generated functions don't just share the final values. CoffeeScript provides the do keyword, which immediately invokes a passed function, forwarding any arguments.

for filename in list  do (filename) ->
    fs.readFile filename, (err, contents) ->
      compile filename, contents.toString()

var filename, _fn, _i, _len;

_fn = function(filename) {
  return fs.readFile(filename, function(err, contents) {
    return compile(filename, contents.toString());
  });
};for (_i = 0, _len = list.length; _i < _len; _i++) {
  filename = list[_i];
  _fn(filename);
}

load

Array Slicing and Splicing with Ranges Ranges can also be used to extract slices of arrays. With two dots (3..6), the range is inclusive (3, 4, 5, 6); with three dots (3...6), the range excludes the end (3, 4, 5). Slices indices have useful defaults. An omitted first index defaults to zero and an omitted second index defaults to the size of the array.

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9]

start   = numbers[0..2]

middle  = numbers[3...-2]

end     = numbers[-2..]

copy    = numbers[..]

var copy, end, middle, numbers, start;

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9];

start = numbers.slice(0, 3);

middle = numbers.slice(3, -2);

end = numbers.slice(-2);

copy = numbers.slice(0);

load

run: middle

The same syntax can be used with assignment to replace a segment of an array with new values, splicing it.

numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

numbers[3..6] = [-3, -4, -5, -6]

var numbers, _ref;

numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];

[].splice.apply(numbers, [3, 4].concat(_ref = [-3, -4, -5, -6])), _ref;

load

run: numbers

Note that JavaScript strings are immutable, and can't be spliced.

Everything is an Expression (at least, as much as possible) You might have noticed how even though we don't add return statements to CoffeeScript functions, they nonetheless return their final value. The CoffeeScript compiler tries to make sure that all statements in the language can be used as expressions. Watch how the return gets pushed down into each possible branch of execution in the function below.

grade = (student) ->
  if student.excellentWork    "A+"
  else if student.okayStuff    if student.triedHard then "B" else "B-"
  else
    "C"eldest = if 24 > 21 then "Liz" else "Ike"

var eldest, grade;

grade = function(student) {
  if (student.excellentWork) {    return "A+";
  } else if (student.okayStuff) {    if (student.triedHard) {      return "B";
    } else {      return "B-";
    }
  } else {    return "C";
  }
};

eldest = 24 > 21 ? "Liz" : "Ike";

load

run: eldest

Even though functions will always return their final value, it's both possible and encouraged to return early from a function body writing out the explicit return (return value), when you know that you're done.

Because variable declarations occur at the top of scope, assignment can be used within expressions, even for variables that haven't been seen before:

six = (one = 1) + (two = 2) + (three = 3)

var one, six, three, two;

six = (one = 1) + (two = 2) + (three = 3);

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run: six

Things that would otherwise be statements in JavaScript, when used as part of an expression in CoffeeScript, are converted into expressions by wrapping them in a closure. This lets you do useful things, like assign the result of a comprehension to a variable:

# 前十个全局属性(变量).globals = (name for name of window)[0...10]

var globals, name;

globals = ((function() {
  var _results;
  _results = [];  for (name in window) {
    _results.push(name);
  }  return _results;
})()).slice(0, 10);

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run: globals

As well as silly things, like passing a try/catch statement directly into a function call:

alert(  try
    nonexistent / undefined
  catch error    "And the error is ... #{error}")

var error;

alert((function() {
  try {    return nonexistent / void 0;
  } catch (_error) {
    error = _error;    return "And the error is ... " + error;
  }
})());

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run

There are a handful of statements in JavaScript that can't be meaningfully converted into expressions, namely break, continue, and return. If you make use of them within a block of code, CoffeeScript won't try to perform the conversion.

Operators and Aliases Because the == operator frequently causes undesirable coercion, is intransitive, and has a different meaning than in other languages, CoffeeScript compiles == into ===, and != into !==. In addition, is compiles into ===, and isnt into !==.

You can use not as an alias for !.

For logic, and compiles to &&, and or into ||.

Instead of a newline or semicolon, then can be used to separate conditions from expressions, in while, if/else, and switch/when statements.

As in YAML, on and yes are the same as boolean true, while off and no are boolean false.

unless can be used as the inverse of if.

As a shortcut for this.property, you can use @property.

You can use in to test for array presence, and of to test for JavaScript object-key presence.

To simplify math expressions, ** can be used for exponentiation, // performs integer division and %% provides true mathematical modulo.

All together now:

CoffeeScript	JavaScript
is	===
isnt	!==
not	!
and	&&
or	||
true, yes, on	true
false, no, off	false
@, this	this
of	in
in	no JS equivalent
a ** b	Math.pow(a, b)
a // b	Math.floor(a / b)
a %% b	(a % b + b) % b

launch() if ignition is onvolume = 10 if band isnt SpinalTap

letTheWildRumpusBegin() unless answer is noif car.speed < limit then accelerate()

winner = yes if pick in [47, 92, 13]print inspect "My name is #{@name}"

var volume, winner;if (ignition === true) {
  launch();
}if (band !== SpinalTap) {
  volume = 10;
}if (answer !== false) {
  letTheWildRumpusBegin();
}if (car.speed < limit) {
  accelerate();
}if (pick === 47 || pick === 92 || pick === 13) {
  winner = true;
}

print(inspect("My name is " + this.name));

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The Existential Operator It's a little difficult to check for the existence of a variable in JavaScript. if (variable) ... comes close, but fails for zero, the empty string, and false. CoffeeScript's existential operator ? returns true unless a variable is null or undefined, which makes it analogous to Ruby's nil?

It can also be used for safer conditional assignment than ||= provides, for cases where you may be handling numbers or strings.

solipsism = true if mind? and not world?

speed = 0speed ?= 15footprints = yeti ? "bear"

var footprints, solipsism, speed;if ((typeof mind !== "undefined" && mind !== null) && (typeof world === "undefined" || world === null)) {
  solipsism = true;
}

speed = 0;if (speed == null) {
  speed = 15;
}

footprints = typeof yeti !== "undefined" && yeti !== null ? yeti : "bear";

load

run: footprints

The accessor variant of the existential operator ?. can be used to soak up null references in a chain of properties. Use it instead of the dot accessor . in cases where the base value may be null or undefined. If all of the properties exist then you'll get the expected result, if the chain is broken, undefined is returned instead of the TypeError that would be raised otherwise.

zip = lottery.drawWinner?().address?.zipcode

var zip, _ref;

zip = typeof lottery.drawWinner === "function" ? (_ref = lottery.drawWinner().address) != null ? _ref.zipcode : void 0 : void 0;

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Soaking up nulls is similar to Ruby's andand gem, and to the safe navigation operator in Groovy.

Classes, Inheritance, and Super JavaScript's prototypal inheritance has always been a bit of a brain-bender, with a whole family tree of libraries that provide a cleaner syntax for classical inheritance on top of JavaScript's prototypes: Base2, Prototype.js, JS.Class, etc. The libraries provide syntactic sugar, but the built-in inheritance would be completely usable if it weren't for a couple of small exceptions: it's awkward to call super (the prototype object's implementation of the current function), and it's awkward to correctly set the prototype chain.

Instead of repetitively attaching functions to a prototype, CoffeeScript provides a basic class structure that allows you to name your class, set the superclass, assign prototypal properties, and define the constructor, in a single assignable expression.

Constructor functions are named, to better support helpful stack traces. In the first class in the example below, this.constructor.name is "Animal".

class Animal
  constructor: (@name) ->

  move: (meters) ->
    alert @name + " moved #{meters}m."class Snake extends Animal
  move: ->
    alert "Slithering..."
    super 5class Horse extends Animal
  move: ->
    alert "Galloping..."
    super 45sam = new Snake "Sammy the Python"tom = new Horse "Tommy the Palomino"sam.move()
tom.move()

var Animal, Horse, Snake, sam, tom,
  __hasProp = {}.hasOwnProperty,
  __extends = function(child, parent) { for (var key in parent) { if (__hasProp.call(parent, key)) child[key] = parent[key]; } function ctor() { this.constructor = child; } ctor.prototype = parent.prototype; child.prototype = new ctor(); child.__super__ = parent.prototype; return child; };

Animal = (function() {
  function Animal(name) {
    this.name = name;
  }

  Animal.prototype.move = function(meters) {
    return alert(this.name + (" moved " + meters + "m."));
  };  return Animal;

})();

Snake = (function(_super) {
  __extends(Snake, _super);  function Snake() {
    return Snake.__super__.constructor.apply(this, arguments);
  }

  Snake.prototype.move = function() {
    alert("Slithering...");    return Snake.__super__.move.call(this, 5);
  };  return Snake;

})(Animal);

Horse = (function(_super) {
  __extends(Horse, _super);  function Horse() {
    return Horse.__super__.constructor.apply(this, arguments);
  }

  Horse.prototype.move = function() {
    alert("Galloping...");    return Horse.__super__.move.call(this, 45);
  };  return Horse;

})(Animal);

sam = new Snake("Sammy the Python");

tom = new Horse("Tommy the Palomino");

sam.move();

tom.move();

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run

If structuring your prototypes classically isn't your cup of tea, CoffeeScript provides a couple of lower-level conveniences. The extends operator helps with proper prototype setup, and can be used to create an inheritance chain between any pair of constructor functions; :: gives you quick access to an object's prototype; and super() is converted into a call against the immediate ancestor's method of the same name.

String::dasherize = ->
  this.replace /_/g, "-"

String.prototype.dasherize = function() {
  return this.replace(/_/g, "-");
};

load

run: "one_two".dasherize()

Finally, class definitions are blocks of executable code, which make for interesting metaprogramming possibilities. Because in the context of a class definition, this is the class object itself (the constructor function), you can assign static properties by using
@property: value, and call functions defined in parent classes: @attr 'title', type: 'text'

Destructuring Assignment To make extracting values from complex arrays and objects more convenient, CoffeeScript implements ECMAScript Harmony's proposed destructuring assignment syntax. When you assign an array or object literal to a value, CoffeeScript breaks up and matches both sides against each other, assigning the values on the right to the variables on the left. In the simplest case, it can be used for parallel assignment:

theBait   = 1000theSwitch = 0[theBait, theSwitch] = [theSwitch, theBait]

var theBait, theSwitch, _ref;

theBait = 1000;

theSwitch = 0;

_ref = [theSwitch, theBait], theBait = _ref[0], theSwitch = _ref[1];

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run: theBait

But it's also helpful for dealing with functions that return multiple values.

weatherReport = (location) ->
  # 发起一个 Ajax 请求获取天气...
  [location, 72, "Mostly Sunny"]

[city, temp, forecast] = weatherReport "Berkeley, CA"

var city, forecast, temp, weatherReport, _ref;

weatherReport = function(location) {
  return [location, 72, "Mostly Sunny"];
};

_ref = weatherReport("Berkeley, CA"), city = _ref[0], temp = _ref[1], forecast = _ref[2];

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run: forecast

Destructuring assignment can be used with any depth of array and object nesting, to help pull out deeply nested properties.

futurists =  sculptor: "Umberto Boccioni"
  painter:  "Vladimir Burliuk"
  poet:    name:   "F.T. Marinetti"
    address: [      "Via Roma 42R"
      "Bellagio, Italy 22021"
    ]

{poet: {name, address: [street, city]}} = futurists

var city, futurists, name, street, _ref, _ref1;

futurists = {
  sculptor: "Umberto Boccioni",
  painter: "Vladimir Burliuk",
  poet: {
    name: "F.T. Marinetti",
    address: ["Via Roma 42R", "Bellagio, Italy 22021"]
  }
};

_ref = futurists.poet, name = _ref.name, (_ref1 = _ref.address, street = _ref1[0], city = _ref1[1]);

load

run: "name + "-" + street"

Destructuring assignment can even be combined with splats.

tag = "<impossible>"[open, contents..., close] = tag.split("")

var close, contents, open, tag, _i, _ref,
  __slice = [].slice;

tag = "<impossible>";

_ref = tag.split(""), open = _ref[0], contents = 3 <= _ref.length ? __slice.call(_ref, 1, _i = _ref.length - 1) : (_i = 1, []), close = _ref[_i++];

load

run: contents.join("")

Expansion can be used to retrieve elements from the end of an array without having to assign the rest of its values. It works in function parameter lists as well.

text = "Every literary critic believes he will
        outwit history and have the last word"[first, ..., last] = text.split " "

var first, last, text, _ref;

text = "Every literary critic believes he will outwit history and have the last word";

_ref = text.split(" "), first = _ref[0], last = _ref[_ref.length - 1];

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run: "first + " " + last"

Destructuring assignment is also useful when combined with class constructors to assign properties to your instance from an options object passed to the constructor.

class Person
  constructor: (options) -> 
    {@name, @age, @height} = options

tim = new Person age: 4

var Person, tim;

Person = (function() {
  function Person(options) {
    this.name = options.name, this.age = options.age, this.height = options.height;
  }  return Person;

})();

tim = new Person({
  age: 4});

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run: tim.age

Function binding In JavaScript, the this keyword is dynamically scoped to mean the object that the current function is attached to. If you pass a function as a callback or attach it to a different object, the original value of this will be lost. If you're not familiar with this behavior, this Digital Web article gives a good overview of the quirks.

The fat arrow => can be used to both define a function, and to bind it to the current value of this, right on the spot. This is helpful when using callback-based libraries like Prototype or jQuery, for creating iterator functions to pass to each, or event-handler functions to use with bind. Functions created with the fat arrow are able to access properties of the this where they're defined.

Account = (customer, cart) ->
  @customer = customer  @cart = cart

  $('.shopping_cart').bind 'click', (event) =>
    @customer.purchase @cart

var Account;

Account = function(customer, cart) {
  this.customer = customer;  this.cart = cart;  return $('.shopping_cart').bind('click', (function(_this) {
    return function(event) {
      return _this.customer.purchase(_this.cart);
    };
  })(this));
};

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If we had used -> in the callback above, @customer would have referred to the undefined "customer" property of the DOM element, and trying to call purchase() on it would have raised an exception.

When used in a class definition, methods declared with the fat arrow will be automatically bound to each instance of the class when the instance is constructed.

Embedded JavaScript Hopefully, you'll never need to use it, but if you ever need to intersperse snippets of JavaScript within your CoffeeScript, you can use backticks to pass it straight through.

hi = `function() {
  return [document.title, "Hello JavaScript"].join(": ");
}`

var hi;

hi = function() {
  return [document.title, "Hello JavaScript"].join(": ");
};

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run: hi()

Switch/When/Else Switch statements in JavaScript are a bit awkward. You need to remember to break at the end of every case statement to avoid accidentally falling through to the default case. CoffeeScript prevents accidental fall-through, and can convert the switch into a returnable, assignable expression. The format is: switch condition, when clauses, else the default case.

As in Ruby, switch statements in CoffeeScript can take multiple values for each when clause. If any of the values match, the clause runs.

switch day  when "Mon" then go work  when "Tue" then go relax  when "Thu" then go iceFishing  when "Fri", "Sat"
    if day is bingoDay
      go bingo
      go dancing  when "Sun" then go church  else go work

switch (day) {  case "Mon":
    go(work);    break;  case "Tue":
    go(relax);    break;  case "Thu":
    go(iceFishing);    break;  case "Fri":  case "Sat":    if (day === bingoDay) {
      go(bingo);
      go(dancing);
    }    break;  case "Sun":
    go(church);    break;  default:
    go(work);
}

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Switch statements can also be used without a control expression, turning them in to a cleaner alternative to if/else chains.

score = 76grade = switch
  when score < 60 then 'F'
  when score < 70 then 'D'
  when score < 80 then 'C'
  when score < 90 then 'B'
  else 'A'# grade == 'C'

var grade, score;

score = 76;

grade = (function() {
  switch (false) {    case !(score < 60):      return 'F';    case !(score < 70):      return 'D';    case !(score < 80):      return 'C';    case !(score < 90):      return 'B';    default:      return 'A';
  }
})();

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Try/Catch/Finally Try/catch statements are just about the same as JavaScript (although they work as expressions).

try
  allHellBreaksLoose()
  catsAndDogsLivingTogether()catch error  print errorfinally
  cleanUp()

var error;try {
  allHellBreaksLoose();
  catsAndDogsLivingTogether();
} catch (_error) {
  error = _error;
  print(error);
} finally {
  cleanUp();
}

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Chained Comparisons CoffeeScript borrows chained comparisons from Python — making it easy to test if a value falls within a certain range.

cholesterol = 127healthy = 200 > cholesterol > 60

var cholesterol, healthy;

cholesterol = 127;

healthy = (200 > cholesterol && cholesterol > 60);

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run: healthy

String Interpolation, Block Strings, and Block Comments Ruby-style string interpolation is included in CoffeeScript. Double-quoted strings allow for interpolated values, using #{ ... }, and single-quoted strings are literal.

author = "Wittgenstein"quote  = "A picture is a fact. -- #{ author }"sentence = "#{ 22 / 7 } is a decent approximation of π"

var author, quote, sentence;

author = "Wittgenstein";

quote = "A picture is a fact. -- " + author;

sentence = "" + (22 / 7) + " is a decent approximation of π";

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run: sentence

Multiline strings are allowed in CoffeeScript. Lines are joined by a single space unless they end with a backslash. Indentation is ignored.

mobyDick = "Call me Ishmael. Some years ago --
  never mind how long precisely -- having little
  or no money in my purse, and nothing particular
  to interest me on shore, I thought I would sail
  about a little and see the watery part of the
  world..."

var mobyDick;

mobyDick = "Call me Ishmael. Some years ago -- never mind how long precisely -- having little or no money in my purse, and nothing particular to interest me on shore, I thought I would sail about a little and see the watery part of the world...";

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run: mobyDick

Block strings can be used to hold formatted or indentation-sensitive text (or, if you just don't feel like escaping quotes and apostrophes). The indentation level that begins the block is maintained throughout, so you can keep it all aligned with the body of your code.

html = """
       <strong>
         cup of coffeescript
       </strong>
       """

var html;

html = "<strong>\n  cup of coffeescript\n</strong>";

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run: html

Double-quoted block strings, like other double-quoted strings, allow interpolation.

Sometimes you'd like to pass a block comment through to the generated JavaScript. For example, when you need to embed a licensing header at the top of a file. Block comments, which mirror the syntax for block strings, are preserved in the generated code.

###
SkinnyMochaHalfCaffScript Compiler v1.0
Released under the MIT License
###

/*
SkinnyMochaHalfCaffScript Compiler v1.0
Released under the MIT License
 */

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Block Regular Expressions Similar to block strings and comments, CoffeeScript supports block regexes — extended regular expressions that ignore internal whitespace and can contain comments and interpolation. Modeled after Perl's /x modifier, CoffeeScript's block regexes are delimited by /// and go a long way towards making complex regular expressions readable. To quote from the CoffeeScript source:

OPERATOR = /// ^ (
  ?: [-=]>             # 函数
   | [-+*/%<>&|^!?=]=  # 复合赋值 / 比较
   | >>>=?             # 补 0 右移
   | ([-+:])\1         # 双写
   | ([&|<>])\2=?      # 逻辑 / 移位
   | \?\.              # soak 访问
   | \.{2,3}           # 范围或者 splat) ///

var OPERATOR;

OPERATOR = /^(?:[-=]>|[-+*\/%<>&|^!?=]=|>>>=?|([-+:])\1|([&|<>])\2=?|\?\.|\.{2,3})/;

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Cake, and Cakefiles

CoffeeScript includes a (very) simple build system similar to Make and Rake. Naturally, it's called Cake, and is used for the tasks that build and test the CoffeeScript language itself. Tasks are defined in a file named Cakefile, and can be invoked by running cake [task] from within the directory. To print a list of all the tasks and options, just type cake.

Task definitions are written in CoffeeScript, so you can put arbitrary code in your Cakefile. Define a task with a name, a long description, and the function to invoke when the task is run. If your task takes a command-line option, you can define the option with short and long flags, and it will be made available in the options object. Here's a task that uses the Node.js API to rebuild CoffeeScript's parser:

fs = require 'fs'option '-o', '--output [DIR]', 'directory for compiled code'task 'build:parser', 'rebuild the Jison parser', (options) ->
  require 'jison'
  code = require('./lib/grammar').parser.generate()
  dir  = options.output or 'lib'
  fs.writeFile "#{dir}/parser.js", code

var fs;

fs = require('fs');

option('-o', '--output [DIR]', 'directory for compiled code');

task('build:parser', 'rebuild the Jison parser', function(options) {
  var code, dir;  require('jison');
  code = require('./lib/grammar').parser.generate();
  dir = options.output || 'lib';  return fs.writeFile("" + dir + "/parser.js", code);
});

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If you need to invoke one task before another — for example, running build before test, you can use the invoke function: invoke 'build'. Cake tasks are a minimal way to expose your CoffeeScript functions to the command line, so don't expect any fanciness built-in. If you need dependencies, or async callbacks, it's best to put them in your code itself — not the cake task.

Source Maps

CoffeeScript 1.6.1 and above include support for generating source maps, a way to tell your JavaScript engine what part of your CoffeeScript program matches up with the code being evaluated. Browsers that support it can automatically use source maps to show your original source code in the debugger. To generate source maps alongside your JavaScript files, pass the --map or -m flag to the compiler.

For a full introduction to source maps, how they work, and how to hook them up in your browser, read the HTML5 Tutorial.

"text/coffeescript" Script Tags

While it's not recommended for serious use, CoffeeScripts may be included directly within the browser using <script type="text/coffeescript"> tags. The source includes a compressed and minified version of the compiler (Download current version here, 39k when gzipped) as extras/coffee-script.js. Include this file on a page with inline CoffeeScript tags, and it will compile and evaluate them in order.

In fact, the little bit of glue script that runs "Try CoffeeScript" above, as well as the jQuery for the menu, is implemented in just this way. View source and look at the bottom of the page to see the example. Including the script also gives you access to CoffeeScript.compile() so you can pop open Firebug and try compiling some strings.

The usual caveats about CoffeeScript apply — your inline scripts will run within a closure wrapper, so if you want to expose global variables or functions, attach them to the window object.

Books

There are a number of excellent resources to help you get started with CoffeeScript, some of which are freely available online.

• The Little Book on CoffeeScript is a brief 5-chapter introduction to CoffeeScript, written with great clarity and precision by Alex MacCaw.

• Smooth CoffeeScript is a reimagination of the excellent book Eloquent JavaScript, as if it had been written in CoffeeScript instead. Covers language features as well as the functional and object oriented programming styles. By E. Hoigaard.

• CoffeeScript: Accelerated JavaScript Development is Trevor Burnham's thorough introduction to the language. By the end of the book, you'll have built a fast-paced multiplayer word game, writing both the client-side and Node.js portions in CoffeeScript.

• CoffeeScript Programming with jQuery, Rails, and Node.js is a new book by Michael Erasmus that covers CoffeeScript with an eye towards real-world usage both in the browser (jQuery) and on the server size (Rails, Node).

• CoffeeScript Ristretto is a deep dive into CoffeeScript's semantics from simple functions up through closures, higher-order functions, objects, classes, combinators, and decorators. By Reg Braithwaite.

• Testing with CoffeeScript is a succinct and freely downloadable guide to building testable applications with CoffeeScript and Jasmine.

• CoffeeScript Application Development is a new book from Packt Publishing that introduces CoffeeScript while walking through the process of building a demonstration web application.

• CoffeeScript in Action is a new book from Manning Publications that covers CoffeeScript syntax, composition techniques and application development.

Screencasts

• A Sip of CoffeeScript is a Code School Course which combines 6 screencasts with in-browser coding to make learning fun. The first level is free to try out.

• Meet CoffeeScript is a 75-minute long screencast by PeepCode. Highly memorable for its animations which demonstrate transforming CoffeeScript into the equivalent JS.

• If you're looking for less of a time commitment, RailsCasts' CoffeeScript Basics should have you covered, hitting all of the important notes about CoffeeScript in 11 minutes.

Examples

The best list of open-source CoffeeScript examples can be found on GitHub. But just to throw out few more:

• github's Hubot, a friendly IRC robot that can perform any number of useful and useless tasks.

• sstephenson's Pow, a zero-configuration Rack server, with comprehensive annotated source.

• technoweenie's Coffee-Resque, a port of Resque for Node.js.

• assaf's Zombie.js, a headless, full-stack, faux-browser testing library for Node.js.

• jashkenas' Underscore.coffee, a port of the Underscore.js library of helper functions.

• stephank's Orona, a remake of the Bolo tank game for modern browsers.

• josh's nack, a Node.js-powered Rack server.

Resources

• Source Code
  Use bin/coffee to test your changes,
  bin/cake test to run the test suite,
  bin/cake build to rebuild the CoffeeScript compiler, and
  bin/cake build:parser to regenerate the Jison parser if you're working on the grammar.
  
  git checkout lib && bin/cake build:full is a good command to run when you're working on the core language. It'll refresh the lib directory (in case you broke something), build your altered compiler, use that to rebuild itself (a good sanity test) and then run all of the tests. If they pass, there's a good chance you've made a successful change.

• CoffeeScript Issues
  Bug reports, feature proposals, and ideas for changes to the language belong here.

• CoffeeScript Google Group
  If you'd like to ask a question, the mailing list is a good place to get help.

• The CoffeeScript Wiki
  If you've ever learned a neat CoffeeScript tip or trick, or ran into a gotcha — share it on the wiki. The wiki also serves as a directory of handy text editor extensions, web framework plugins, and general CoffeeScript build tools.

• The FAQ
  Perhaps your CoffeeScript-related question has been asked before. Check the FAQ first.

• JS2Coffee
  Is a very well done reverse JavaScript-to-CoffeeScript compiler. It's not going to be perfect (infer what your JavaScript classes are, when you need bound functions, and so on...) — but it's a great starting point for converting simple scripts.

• High-Rez Logo
  The CoffeeScript logo is available in Illustrator, EPS and PSD formats, for use in presentations.

Web Chat (IRC)

Quick help and advice can usually be found in the CoffeeScript IRC room. Join #coffeescript on irc.freenode.net, or click the button below to open a webchat session on this page.

click to open #coffeescript

Change Log

1.7.1 – January 29, 2014

• Fixed a typo that broke node module lookup when running a script directly with the coffee binary.

1.7.0 – January 28, 2014

• When requiring CoffeeScript files in Node you must now explicitly register the compiler. This can be done with require 'coffee-script/register' or CoffeeScript.register(). Also for configuration such as Mocha's, use coffee-script/register.

• Improved error messages, source maps and stack traces. Source maps now use the updated //# syntax.

• Leading . now closes all open calls, allowing for simpler chaining syntax.

$ 'body'.click (e) ->
  $ '.box'
  .fadeIn 'fast'
  .addClass '.active'.css 'background', 'white'

$('body').click(function(e) {
  return $('.box').fadeIn('fast').addClass('.active');
}).css('background', 'white');

load

• Added **, // and %% operators and ... expansion in parameter lists and destructuring expressions.

• Multiline strings are now joined by a single space and ignore all indentation. A backslash at the end of a line can denote the amount of whitespace between lines, in both strings and heredocs. Backslashes correctly escape whitespace in block regexes.

• Closing brackets can now be indented and therefore no longer cause unexpected error.

• Several breaking compilation fixes. Non-callable literals (strings, numbers etc.) don't compile in a call now and multiple postfix conditionals compile properly. Postfix conditionals and loops always bind object literals. Conditional assignment compiles properly in subexpressions. super is disallowed outside of methods and works correctly inside for loops.

• Formatting of compiled block comments has been improved.

• No more -p folders on Windows.

• The options object passed to CoffeeScript is no longer mutated.

1.6.3 – June 2, 2013

• The CoffeeScript REPL now remembers your history between sessions. Just like a proper REPL should.

• You can now use require in Node to load .coffee.md Literate CoffeeScript files. In the browser, text/literate-coffeescript script tags.

• The old coffee --lint command has been removed. It was useful while originally working on the compiler, but has been surpassed by JSHint. You may now use -l to pass literate files in over stdio.

• Bugfixes for Windows path separators, catch without naming the error, and executable-class-bodies-with- prototypal-property-attachment.

1.6.2 – March 18, 2013

• Source maps have been used to provide automatic line-mapping when running CoffeeScript directly via the coffee command, and for automatic line-mapping when running CoffeeScript directly in the browser. Also, to provide better error messages for semantic errors thrown by the compiler — with colors, even.

• Improved support for mixed literate/vanilla-style CoffeeScript projects, and generating source maps for both at the same time.

• Fixes for 1.6.x regressions with overriding inherited bound functions, and for Windows file path management.

• The coffee command can now correctly fork() both .coffee and .js files. (Requires Node.js 0.9+)

1.6.1 – March 5, 2013

• First release of source maps. Pass the --map flag to the compiler, and off you go. Direct all your thanks over to Jason Walton.

• Fixed a 1.5.0 regression with multiple implicit calls against an indented implicit object. Combinations of implicit function calls and implicit objects should generally be parsed better now — but it still isn't good style to nest them too heavily.

• .coffee.md is now also supported as a Literate CoffeeScript file extension, for existing tooling. .litcoffee remains the canonical one.

• Several minor fixes surrounding member properties, bound methods and super in class declarations.

1.5.0 – Feb 25, 2013

• First release of Literate CoffeeScript.

• The CoffeeScript REPL is now based on the Node.js REPL, and should work better and more familiarly.

• Returning explicit values from constructors is now forbidden. If you want to return an arbitrary value, use a function, not a constructor.

• You can now loop over an array backwards, without having to manually deal with the indexes: for item in list by -1

• Source locations are now preserved in the CoffeeScript AST, although source maps are not yet being emitted.

1.4.0 – Oct 23, 2012

• The CoffeeScript compiler now strips Microsoft's UTF-8 BOM if it exists, allowing you to compile BOM-borked source files.

• Fix Node/compiler deprecation warnings by removing registerExtension, and moving from path.exists to fs.exists.

• Small tweaks to splat compilation, backticks, slicing, and the error for duplicate keys in object literals.

1.3.3 – May 15, 2012

• Due to the new semantics of JavaScript's strict mode, CoffeeScript no longer guarantees that constructor functions have names in all runtimes. See #2052 for discussion.

• Inside of a nested function inside of an instance method, it's now possible to call super more reliably (walks recursively up).

• Named loop variables no longer have different scoping heuristics than other local variables. (Reverts #643)

• Fix for splats nested within the LHS of destructuring assignment.

• Corrections to our compile time strict mode forbidding of octal literals.

1.3.1 – April 10, 2012

• CoffeeScript now enforces all of JavaScript's Strict Mode early syntax errors at compile time. This includes old-style octal literals, duplicate property names in object literals, duplicate parameters in a function definition, deleting naked variables, setting the value of eval or arguments, and more. See a full discussion at #1547.

• The REPL now has a handy new multi-line mode for entering large blocks of code. It's useful when copy-and-pasting examples into the REPL. Enter multi-line mode with Ctrl-V. You may also now pipe input directly into the REPL.

• CoffeeScript now prints a Generated by CoffeeScript VERSION header at the top of each compiled file.

• Conditional assignment of previously undefined variables a or= b is now considered a syntax error.

• A tweak to the semantics of do, which can now be used to more easily simulate a namespace: do (x = 1, y = 2) -> ...

• Loop indices are now mutable within a loop iteration, and immutable between them.

• Both endpoints of a slice are now allowed to be omitted for consistency, effectively creating a shallow copy of the list.

• Additional tweaks and improvments to coffee --watch under Node's "new" file watching API. Watch will now beep by default if you introduce a syntax error into a watched script. We also now ignore hidden directories by default when watching recursively.

1.2.0 – Dec. 18, 2011

• Multiple improvements to coffee --watch and --join. You may now use both together, as well as add and remove files and directories within a --watch'd folder.

• The throw statement can now be used as part of an expression.

• Block comments at the top of the file will now appear outside of the safety closure wrapper.

• Fixed a number of minor 1.1.3 regressions having to do with trailing operators and unfinished lines, and a more major 1.1.3 regression that caused bound functions within bound class functions to have the incorrect this.

1.1.3 – Nov. 8, 2011

• Ahh, whitespace. CoffeeScript's compiled JS now tries to space things out and keep it readable, as you can see in the examples on this page.

• You can now call super in class level methods in class bodies, and bound class methods now preserve their correct context.

• JavaScript has always supported octal numbers 010 is 8, and hexadecimal numbers 0xf is 15, but CoffeeScript now also supports binary numbers: 0b10 is 2.

• The CoffeeScript module has been nested under a subdirectory to make it easier to require individual components separately, without having to use npm. For example, after adding the CoffeeScript folder to your path: require('coffee-script/lexer')

• There's a new "link" feature in Try CoffeeScript on this webpage. Use it to get a shareable permalink for your example script.

• The coffee --watch feature now only works on Node.js 0.6.0 and higher, but now also works properly on Windows.

• Lots of small bug fixes from @michaelficarra, @geraldalewis, @satyr , and @trevorburnham.

1.1.2 – August 4, 2011 Fixes for block comment formatting, ?= compilation, implicit calls against control structures, implicit invocation of a try/catch block, variadic arguments leaking from local scope, line numbers in syntax errors following heregexes, property access on parenthesized number literals, bound class methods and super with reserved names, a REPL overhaul, consecutive compiled semicolons, block comments in implicitly called objects, and a Chrome bug.

1.1.1 – May 10, 2011 Bugfix release for classes with external constructor functions, see issue #1182.

1.1.0 – May 1, 2011 When running via the coffee executable, process.argv and friends now report coffee instead of node. Better compatibility with Node.js 0.4.x module lookup changes. The output in the REPL is now colorized, like Node's is. Giving your concatenated CoffeeScripts a name when using --join is now mandatory. Fix for lexing compound division /= as a regex accidentally. All text/coffeescript tags should now execute in the order they're included. Fixed an issue with extended subclasses using external constructor functions. Fixed an edge-case infinite loop in addImplicitParentheses. Fixed exponential slowdown with long chains of function calls. Globals no longer leak into the CoffeeScript REPL. Splatted parameters are declared local to the function.

1.0.1 – Jan 31, 2011 Fixed a lexer bug with Unicode identifiers. Updated REPL for compatibility with Node.js 0.3.7. Fixed requiring relative paths in the REPL. Trailing return and return undefined are now optimized away. Stopped requiring the core Node.js "util" module for back-compatibility with Node.js 0.2.5. Fixed a case where a conditional return would cause fallthrough in a switch statement. Optimized empty objects in destructuring assignment.

1.0.0 – Dec 24, 2010 CoffeeScript loops no longer try to preserve block scope when functions are being generated within the loop body. Instead, you can use the do keyword to create a convenient closure wrapper. Added a --nodejs flag for passing through options directly to the node executable. Better behavior around the use of pure statements within expressions. Fixed inclusive slicing through -1, for all browsers, and splicing with arbitrary expressions as endpoints.

0.9.6 – Dec 6, 2010 The REPL now properly formats stacktraces, and stays alive through asynchronous exceptions. Using --watch now prints timestamps as files are compiled. Fixed some accidentally-leaking variables within plucked closure-loops. Constructors now maintain their declaration location within a class body. Dynamic object keys were removed. Nested classes are now supported. Fixes execution context for naked splatted functions. Bugfix for inversion of chained comparisons. Chained class instantiation now works properly with splats.

0.9.5 – Nov 21, 2010 0.9.5 should be considered the first release candidate for CoffeeScript 1.0. There have been a large number of internal changes since the previous release, many contributed from satyr's Coco dialect of CoffeeScript. Heregexes (extended regexes) were added. Functions can now have default arguments. Class bodies are now executable code. Improved syntax errors for invalid CoffeeScript. undefined now works like null, and cannot be assigned a new value. There was a precedence change with respect to single-line comprehensions: result = i for i in list
used to parse as result = (i for i in list) by default ... it now parses as
(result = i) for i in list.

0.9.4 – Sep 21, 2010 CoffeeScript now uses appropriately-named temporary variables, and recycles their references after use. Added require.extensions support for Node.js 0.3. Loading CoffeeScript in the browser now adds just a single CoffeeScript object to global scope. Fixes for implicit object and block comment edge cases.

0.9.3 – Sep 16, 2010 CoffeeScript switch statements now compile into JS switch statements — they previously compiled into if/else chains for JavaScript 1.3 compatibility. Soaking a function invocation is now supported. Users of the RubyMine editor should now be able to use --watch mode.

0.9.2 – Aug 23, 2010 Specifying the start and end of a range literal is now optional, eg. array[3..]. You can now say a not instanceof b. Fixed important bugs with nested significant and non-significant indentation (Issue #637). Added a --require flag that allows you to hook into the coffee command. Added a custom jsl.conf file for our preferred JavaScriptLint setup. Sped up Jison grammar compilation time by flattening rules for operations. Block comments can now be used with JavaScript-minifier-friendly syntax. Added JavaScript's compound assignment bitwise operators. Bugfixes to implicit object literals with leading number and string keys, as the subject of implicit calls, and as part of compound assignment.

0.9.1 – Aug 11, 2010 Bugfix release for 0.9.1. Greatly improves the handling of mixed implicit objects, implicit function calls, and implicit indentation. String and regex interpolation is now strictly #{ ... } (Ruby style). The compiler now takes a --require flag, which specifies scripts to run before compilation.

0.9.0 – Aug 4, 2010 The CoffeeScript 0.9 series is considered to be a release candidate for 1.0; let's give her a shakedown cruise. 0.9.0 introduces a massive backwards-incompatible change: Assignment now uses =, and object literals use :, as in JavaScript. This allows us to have implicit object literals, and YAML-style object definitions. Half assignments are removed, in favor of +=, or=, and friends. Interpolation now uses a hash mark # instead of the dollar sign $ — because dollar signs may be part of a valid JS identifier. Downwards range comprehensions are now safe again, and are optimized to straight for loops when created with integer endpoints. A fast, unguarded form of object comprehension was added: for all key, value of object. Mentioning the super keyword with no arguments now forwards all arguments passed to the function, as in Ruby. If you extend class B from parent class A, if A has an extended method defined, it will be called, passing in B — this enables static inheritance, among other things. Cleaner output for functions bound with the fat arrow. @variables can now be used in parameter lists, with the parameter being automatically set as a property on the object — useful in constructors and setter functions. Constructor functions can now take splats.

0.7.2 – Jul 12, 2010 Quick bugfix (right after 0.7.1) for a problem that prevented coffee command-line options from being parsed in some circumstances.

0.7.1 – Jul 11, 2010 Block-style comments are now passed through and printed as JavaScript block comments -- making them useful for licenses and copyright headers. Better support for running coffee scripts standalone via hashbangs. Improved syntax errors for tokens that are not in the grammar.

0.7.0 – Jun 28, 2010 Official CoffeeScript variable style is now camelCase, as in JavaScript. Reserved words are now allowed as object keys, and will be quoted for you. Range comprehensions now generate cleaner code, but you have to specify by -1 if you'd like to iterate downward. Reporting of syntax errors is greatly improved from the previous release. Running coffee with no arguments now launches the REPL, with Readline support. The <- bind operator has been removed from CoffeeScript. The loop keyword was added, which is equivalent to a while true loop. Comprehensions that contain closures will now close over their variables, like the semantics of a forEach. You can now use bound function in class definitions (bound to the instance). For consistency, a in b is now an array presence check, and a of b is an object-key check. Comments are no longer passed through to the generated JavaScript.

0.6.2 – May 15, 2010 The coffee command will now preserve directory structure when compiling a directory full of scripts. Fixed two omissions that were preventing the CoffeeScript compiler from running live within Internet Explorer. There's now a syntax for block comments, similar in spirit to CoffeeScript's heredocs. ECMA Harmony DRY-style pattern matching is now supported, where the name of the property is the same as the name of the value: {name, length}: func. Pattern matching is now allowed within comprehension variables. unless is now allowed in block form. until loops were added, as the inverse of while loops. switch statements are now allowed without switch object clauses. Compatible with Node.js v0.1.95.

0.6.1 – Apr 12, 2010 Upgraded CoffeeScript for compatibility with the new Node.js v0.1.90 series.

0.6.0 – Apr 3, 2010 Trailing commas are now allowed, a-la Python. Static properties may be assigned directly within class definitions, using @property notation.

0.5.6 – Mar 23, 2010 Interpolation can now be used within regular expressions and heredocs, as well as strings. Added the <- bind operator. Allowing assignment to half-expressions instead of special ||=-style operators. The arguments object is no longer automatically converted into an array. After requiring coffee-script, Node.js can now directly load .coffee files, thanks to registerExtension. Multiple splats can now be used in function calls, arrays, and pattern matching.

0.5.5 – Mar 8, 2010 String interpolation, contributed by Stan Angeloff. Since --run has been the default since 0.5.3, updating --stdio and --eval to run by default, pass --compile as well if you'd like to print the result.

0.5.4 – Mar 3, 2010 Bugfix that corrects the Node.js global constants __filename and __dirname. Tweaks for more flexible parsing of nested function literals and improperly-indented comments. Updates for the latest Node.js API.

0.5.3 – Feb 27, 2010 CoffeeScript now has a syntax for defining classes. Many of the core components (Nodes, Lexer, Rewriter, Scope, Optparse) are using them. Cakefiles can use optparse.coffee to define options for tasks. --run is now the default flag for the coffee command, use --compile to save JavaScripts. Bugfix for an ambiguity between RegExp literals and chained divisions.

0.5.2 – Feb 25, 2010 Added a compressed version of the compiler for inclusion in web pages as
extras/coffee-script.js. It'll automatically run any script tags with type text/coffeescript for you. Added a --stdio option to the coffee command, for piped-in compiles.

0.5.1 – Feb 24, 2010 Improvements to null soaking with the existential operator, including soaks on indexed properties. Added conditions to while loops, so you can use them as filters with when, in the same manner as comprehensions.

0.5.0 – Feb 21, 2010 CoffeeScript 0.5.0 is a major release, While there are no language changes, the Ruby compiler has been removed in favor of a self-hosting compiler written in pure CoffeeScript.

0.3.2 – Feb 8, 2010 @property is now a shorthand for this.property.
Switched the default JavaScript engine from Narwhal to Node.js. Pass the --narwhal flag if you'd like to continue using it.

0.3.0 – Jan 26, 2010 CoffeeScript 0.3 includes major syntax changes:
The function symbol was changed to ->, and the bound function symbol is now =>.
Parameter lists in function definitions must now be wrapped in parentheses.
Added property soaking, with the ?. operator.
Made parentheses optional, when invoking functions with arguments.
Removed the obsolete block literal syntax.

0.2.6 – Jan 17, 2010 Added Python-style chained comparisons, the conditional existence operator ?=, and some examples from Beautiful Code. Bugfixes relating to statement-to-expression conversion, arguments-to-array conversion, and the TextMate syntax highlighter.

0.2.5 – Jan 13, 2010 The conditions in switch statements can now take multiple values at once — If any of them are true, the case will run. Added the long arrow ==>, which defines and immediately binds a function to this. While loops can now be used as expressions, in the same way that comprehensions can. Splats can be used within pattern matches to soak up the rest of an array.

0.2.4 – Jan 12, 2010 Added ECMAScript Harmony style destructuring assignment, for dealing with extracting values from nested arrays and objects. Added indentation-sensitive heredocs for nicely formatted strings or chunks of code.

0.2.3 – Jan 11, 2010 Axed the unsatisfactory ino keyword, replacing it with of for object comprehensions. They now look like: for prop, value of object.

0.2.2 – Jan 10, 2010 When performing a comprehension over an object, use ino, instead of in, which helps us generate smaller, more efficient code at compile time.
Added :: as a shorthand for saying .prototype.
The "splat" symbol has been changed from a prefix asterisk *, to a postfix ellipsis ...
Added JavaScript's in operator, empty return statements, and empty while loops.
Constructor functions that start with capital letters now include a safety check to make sure that the new instance of the object is returned.
The extends keyword now functions identically to goog.inherits in Google's Closure Library.

0.2.1 – Jan 5, 2010 Arguments objects are now converted into real arrays when referenced.

0.2.0 – Jan 5, 2010 Major release. Significant whitespace. Better statement-to-expression conversion. Splats. Splice literals. Object comprehensions. Blocks. The existential operator. Many thanks to all the folks who posted issues, with special thanks to Liam O'Connor-Davis for whitespace and expression help.

0.1.6 – Dec 27, 2009 Bugfix for running coffee --interactive and --run from outside of the CoffeeScript directory. Bugfix for nested function/if-statements.

0.1.5 – Dec 26, 2009 Array slice literals and array comprehensions can now both take Ruby-style ranges to specify the start and end. JavaScript variable declaration is now pushed up to the top of the scope, making all assignment statements into expressions. You can use \ to escape newlines. The coffee-script command is now called coffee.

0.1.4 – Dec 25, 2009 The official CoffeeScript extension is now .coffee instead of .cs, which properly belongs to C#. Due to popular demand, you can now also use = to assign. Unlike JavaScript, = can also be used within object literals, interchangeably with :. Made a grammatical fix for chained function calls like func(1)(2)(3)(4). Inheritance and super no longer use __proto__, so they should be IE-compatible now.

0.1.3 – Dec 25, 2009 The coffee command now includes --interactive, which launches an interactive CoffeeScript session, and --run, which directly compiles and executes a script. Both options depend on a working installation of Narwhal. The aint keyword has been replaced by isnt, which goes together a little smoother with is. Quoted strings are now allowed as identifiers within object literals: eg. {"5+5": 10}. All assignment operators now use a colon: +:, -:, *:, etc.

0.1.2 – Dec 24, 2009 Fixed a bug with calling super() through more than one level of inheritance, with the re-addition of the extends keyword. Added experimental Narwhal support (as a Tusk package), contributed by Tom Robinson, including bin/cs as a CoffeeScript REPL and interpreter. New --no-wrap option to suppress the safety function wrapper.

0.1.1 – Dec 24, 2009 Added instanceof and typeof as operators.

0.1.0 – Dec 24, 2009 Initial CoffeeScript release.