/**
* 获取某对象,对应深度的值
* var data = {
* "level_1":{
* "level_2":"value"
* }
* }
* subfield(data,"level_1.level_2") //"value"
*/
function subfield(data,f){
if(f.substr) f = f.split(/\.|\\|\//);
return f.length?arguments.callee(data[f.shift()],f):data;
}