coffeescript中的for-in和for-of

coffee> for k, v in {a:1, b:2} then console.log(k,v)
[]
coffee> for k, v of {a:1, b:2} then console.log(k,v)
a 1
b 2
[ undefined, undefined ]
coffee> for k, v of [1,2] then console.log(k,v)
0 1
1 2
[ undefined, undefined ]
coffee> for k, v in [1,2] then console.log(k,v)
1 0
2 1
[ undefined, undefined ]

 for-in用于数组，for-of 用于object。

for-in中，可通过for value, index in list的形式利用数组下标。