js es6 将对象转换成集合

1、采用 Object.entries(cityMap)

var cityMap = {
        "北京市": "110100",
        "天津市": "120100",
        "上海市": "310100",
      }
var arr=Object.entries(cityMap)
返回的结果是 
0: (2) ["北京市", "110100"]
1: (2) ["天津市", "120100"]
2: (2) ["上海市", "310100"]

2、采用 Object.values(cityMap)

var cityMap = {
        "北京市": "110100",
        "天津市": "120100",
        "上海市": "310100",
      }
var arr=Object.values(cityMap)
返回的结果是 
["110100", "120100", "310100"]