coffescript

GitHub上好多项目都是用coffee-script写的，尤其是运行于Nodejs下的项目，也没太在意，一直没有仔细看看coffee。我学习编程主要还是兴趣驱动，我之前对OT（google wave，etherpad等实时编辑器的核心）很感兴趣，这个项目ShareJs，用coffee实现了类似etherpad的功能，我要看代码，必须了解下coffee了

1.coffee-script在线测试

如果安装了Nodejs，直接在命令行下面跑最好了，这里提供了一个简单的线上测试环境

http://jashkenas.github.com/coffee-script/ 单击TRY COFFEESCRIPT

2.语法

coffee最终是转化为js执行的，不去关注转化后的代码，那么如何写coffee-script呢？

函数定义：

hi = (a,b) ->
  alert(a+" say to:"+b+",hello!");

右边会自动生成编译后真正执行的javascript（后面不再列出）

var hi;
hi = function(a, b) {
  return alert(a + " say to:" + b + ",hello!");
};

函数调用:不用括号

hi "tom","Lily"

字符

内插字符:

name = "tom"
s = "hi #{name}"
alert name

/*跨越多行的字符，类似Python的语法*/
name = "tom
,john
,kinas
"
s = "hi #{name}"
alert name

定义数组

a = [1,2,3,4];/*第一种方法定义*/
b = [ i for i in [1..10]];/*第二种方法,用 ‘..’ 表示范围*/
alert a;
alert b;

遍历数组

a = [1,2,3,4];
b = [ i for i in a];/*很自然的遍历方式*/
alert b;

还可以调用函数:

[alert i for i in a]

this：在coffe没有显示的this,@代替之

sayHello (name)->
  @name = name
  @say -> alert name

对应的javascript：

sayHello(function(name) {
  this.name = name;
  return this.say(function() {
    return alert(name);
  });
});

一行函数调用，带判断

alert "I knew it!" if elvis?

coffee-script 的继承(摘自这里)

class Animal
    constructor: (@name) ->

    move: (meters) ->
        alert @name + " moved " + meters + "m."

class Snake extends Animal
    move: ->
        alert "Slithering..."
        super 5

观察生成的javascript，可以窥探其继承的实现

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