JS - 遍历对象属性

栗子：

var obj = {
  "name": "Poly",
  "career": "it"
}
Object.defineProperty(
obj, "age", 
{ value:"forever 18", enumerable:false }
);
Object.prototype.protoPer1 = function(){console.log("proto");};
Object.prototype.protoPer2 = 2;

for in

用于遍历对象的可枚举属性，包括自有属性、继承自原型的属性

for(var a in obj){
  console.log(a);
}
//输出：name, career, protoPer1, protoPer2

Object.keys

返回一个数组，元素均为对象自有的可枚举属性

console.log(Object.keys(obj));
//输出：["name", "career"]

Object.getOwnProperty

用于返回对象的自有属性，包括可枚举和不可枚举的

console.log(Object.getOwnPropertyNames(obj));
//输出：["name", "career", "age"]