第一次听说CoffeeScript是Rails 3.1将它作为默认的支持，第二次深入的理解是Nodejs的兴起，CoffeeScript用它独特的语法样式，使我这个面向对象出身的程序员在写JavaScript时找到了似曾相识的感觉。当然如果对它的理解仅仅停留在语法的简化，那么只能说对JS(The World’s Most Misunderstood Programming Language)本身并不熟悉。
« JavaScript语言精粹 »一书中提交了很多JS本身语法存在的缺陷，例如全局变量，分号自动补全，==等。CoffeeScript的golden rule是“It’s just JavaScript”, 但是它如何避免这些陷阱，则从另一方面体现了它的强大。本文将从语法强大方面来举例分析。 READMORE 1）函数默认参数 + 字符串连接
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favorite = function(language){
if(language == null){
language = 'CoffeeScript';
}
console.log("I love " + language + " best");
}
favorite()
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favorite = (language = 'CoffeeScript') -> console.log "I love #{language} best"
2）可变参数Splats
这样一个例子：足球赛事中，一般的排名是，冠军，亚军，和其他球队，这里再复杂一点，加上最后一名。也就是：
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Given
allTeams = ['Chelsea', 'Bayern', 'Barcelona', 'Real Madrid', 'Milan', 'Inter', 'HengDa']
Output:
champaion: Chelsea
runner-up: Bayern
others:Barcelona, Real Madrid, Milan, Inter
last:HengDa
用JS和CoffeeScript分别实现
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var allTeams = ['Chelsea', 'Bayern', 'Barcelona', 'Real Madrid', 'Milan', 'Inter', 'HengDa'];
order = function(teams) {
var champion = teams[0];
var runnerup = teams[1];
var others = teams.length >= 3 ? teams.slice(2, teams.length - 1) : [];
var last = teams[teams.length - 1];
console.log("Champion is " + champion);
console.log("Runnerup is " + runnerup);
console.log("others are " + others);
console.log("last is " + last);
};
order(allTeams);
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allTeams = [
'Chelsea'
'Bayern'
'Barcelona'
'Real Madrid'
'Milan'
'Inter'
'HengDa'
]
order = (champion, runnerup, others..., last) ->
console.log "Champion is #{champion}"
console.log "Runnerup is #{runnerup}"
console.log "others are #{others}"
console.log "last is #{last}"
order allTeams...
3）Destructing Assignment
在Ruby中有同样的语法，下面的例子实现了Fibonacci数列
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#Fibonacci
[last, current] = [0,1]
for i in [0..10]
console.log last
[last, current] = [current, current + last]
console.log last
更加强大的是当右侧是一个对象时，会根据该对象的属性进行赋值：
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class Shape
constructor: (@width) ->
computeArea: -> throw new Error('I am an abstract class!')
class Square extends Shape
computeArea: -> Math.pow @width, 2
class Circle extends Shape
radius: -> @width / 2
computeArea: -> Math.PI * Math.pow @radius(), 2
#The instanceof operator tests presence of constructor.prototype in object prototype chain.
showArea = (shape) ->
unless shape instanceof Shape
throw new Error('showArea requires a Shape instance!')
console.log shape.computeArea()
showArea new Square(2) # 4
showArea new Circle(2) # pi
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myRect =
x: 100
y: 200
{x: myX, y: myY} = myRect
#定义了myX和myY两个变量，并调用myRect.x和myRect.y分别赋值
console.log myX
console.log myY
#当定义的变量名称与右侧对象的key值相同时，可以更精简为
{x, y} = myRect
console.log x
console.log y
4）class与inheritance 定义了class与extends来是语法来包装JS使其更加类似面向对象的语言。给个简单例子
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class Shape
constructor: (@width) ->
computeArea: -> throw new Error('I am an abstract class!')
class Square extends Shape
computeArea: -> Math.pow @width, 2
class Circle extends Shape
radius: -> @width / 2
computeArea: -> Math.PI * Math.pow @radius(), 2
#The instanceof operator tests presence of constructor.prototype in object prototype chain.
showArea = (shape) ->
unless shape instanceof Shape
throw new Error('showArea requires a Shape instance!')
console.log shape.computeArea()
showArea new Square(2) # 4
showArea new Circle(2) # pi