JS如何获取对象键值对中key值的方法

Object.keys(obj)

// simple array
var arr = ['a', 'b', 'c'];
console.log(Object.keys(arr)); // console: ['0', '1', '2']
// array like object
var obj = { 0: 'a', 1: 'b', 2: 'c' };
console.log(Object.keys(obj)); // console: ['0', '1', '2']
// array like object with random key ordering
var anObj = { 100: 'a', 2: 'b', 7: 'c' };
console.log(Object.keys(anObj)); // console: ['2', '7', '100']
// getFoo is a property which isn't enumerable
var myObj = Object.create({}, {
  getFoo: {
    value: function () { return this.foo; }
  } 
});
myObj.foo = 1;
console.log(Object.keys(myObj)); // console: ['foo']

Object.keys("foo");
// TypeError: "foo" is not an object (ES5 code)
Object.keys("foo");
// ["0", "1", "2"]                   (ES2015 code)

if (!Object.keys) {
  Object.keys = (function () {
    var hasOwnProperty = Object.prototype.hasOwnProperty,
        hasDontEnumBug = !({toString: null}).propertyIsEnumerable('toString'),
        dontEnums = [
          'toString',
          'toLocaleString',
          'valueOf',
          'hasOwnProperty',
          'isPrototypeOf',
          'propertyIsEnumerable',
          'constructor'
        ],
        dontEnumsLength = dontEnums.length;
    return function (obj) {
      if (typeof obj !== 'object' && typeof obj !== 'function' || obj === null) throw new TypeError('Object.keys called on non-object');
      var result = [];
      for (var prop in obj) {
        if (hasOwnProperty.call(obj, prop)) result.push(prop);
      }
      if (hasDontEnumBug) {
        for (var i=0; i < dontEnumsLength; i++) {
          if (hasOwnProperty.call(obj, dontEnums[i])) result.push(dontEnums[i]);
        }
      }
      return result;
    }
  })()
};

       	 Object  obj=  restTemplate.getForObject("https://api.weixin.qq.com/sns/jscode2session?appid=自己的AppID&secret=自己的秘钥&js_code=" +code + "&grant_type=authorization_code",String.class);
     //转换成String
        	String object1 = obj.toString();
        	JSONObject json=new JSONObject(object1);
               Map<String,Object> map=new HashMap<String, Object>();
               Iterator it = json.keys();
               while (it.hasNext()) {
                   String key = (String) it.next();
                       Object value = json.get(key);
                       map.put(key, value);
               }
               String openid = (String) map.get("openid");