flat an object

flatObject.js

var person = {
  name : {
    first : 'ye',
    last : 'lin'
  },
  age : 28,
  gender : 'male',
  birth : {
    year : 1987,
    month : 6,
    date : 15
  },
  education : {
    college : 'zzu',
    graduate : 'bupt',
    middle : {
      junior : 'ny26',
      senior : 'nyyz'
    }
  }
}

var flat = function(obj){
  var result = {};
  function fn(obj, prev) {
    var key, val;
    for(key in obj){
      if(obj.hasOwnProperty(key)){
        val = obj[key];
        if(typeof val === 'object'){
          if(prev){
            fn(val, prev + '.' + key);
          }else{
            fn(val, key);
          }
        }else{
          if(prev){
            result[prev + '.' + key] = val;
          }else{
            result[key] = val;
          }
        }
      }
    }
  }
  fn(obj);
  return result;
}
console.log(flat(person));