coffeescript遍历json对象.

直接给代码：

[python] view plaincopy在CODE上查看代码片派生到我的代码片
headers = a:”this is a”
,b:”this is b”
,c:”this is c”

exheaders = e : “this is e”,c:”this is c”

headers[key] = value for key,value of exheaders

alert “key:#{key},value:#{value}” for key,value of headers

for i in headers
headers[i] = exheaders[i]

这个例子中，有两个JSON对象：headers，exheaders。遍历的方法为：
for key,value of …

以上代码编译成javascript为：

[javascript] view plaincopy在CODE上查看代码片派生到我的代码片
var exheaders, headers, key, value;

headers = {
a: “this is a”,
b: “this is b”,
c: “this is c”
};

exheaders = {
e: “this is e”,
c: “this is c”
};

for (key in exheaders) {
value = exheaders[key];
headers[key] = value;
}

for (key in headers) {
value = headers[key];
alert(“key:” + key + “,value:” + value);
}
从中也可以看到javascript遍历json的方法。使用for(var i = 0; i < json对象.length;i++)的方法是行不通的，因为json对象没有length的属性
所以，coffeescript下，遍历json对象的方法不能写成：

for i in headers
headers[i] = exheaders[i]

它会编译成：

[javascript] view plaincopy在CODE上查看代码片派生到我的代码片
for (_i = 0, _len = headers.length; _i < _len; _i++) {
i = headers[_i];
headers[i] = exheaders[i];
}