js判断对象的某个属性是否存在

参考：https://www.jb51.net/article/141994.htm

原始数据，

[

    {"name":"向阳镇","id":"10","pId":0,"open": "true"},

    {"name":"彩蓝桥镇","id":"20","pId":0,"open": "true"},

    {"name":"丁向镇","id":"30","pId":0,"open": "true"},  

    {"name":"桃园东","id":"1","lng":"120.56934479","lat":31.85618831,"region":"向阳河","pId":10,"waterQuality":"I"},

    {"name":"董家桥村","id":"2","lng":"120.56709498","lat":31.90134260,"region":"向阳河","pId":10,"waterQuality":"II"},

    {"name":"庄上村","id":"3","lng":"120.55362585","lat":31.87984724,"region":"彩蓝桥河","pId":20,"waterQuality":"III"},

    {"name":"绣品街","id":"4","lng":"120.53118860","lat":31.86526444,"region":"彩蓝桥河","pId":20,"waterQuality":"IV"},

    {"name":"下村","id":"5","lng":"120.57111579","lat":31.85730531,"region":"丁向河","pId":30,"waterQuality":"V"}

]

处理过程，给不存在的属性赋值，赋值之后，该对象不存在的属性就存在了

var getData = response.data;
      for(let i=0;i<getData.length;i++){
         if(getData[i].open == undefined){ getData[i].open =""; }
         if(getData[i].lng == undefined){ getData[i].lng =""; }
         if(getData[i].lat == undefined){ getData[i].lat =""; }
         if(getData[i].region == undefined){ getData[i].region =""; }
         if(getData[i].waterQuality == undefined){ getData[i].waterQuality=""; }
      }

处理之后数据

[
    {"name":"向阳镇",  "id":"10", "pId":0,  "open": "true",   "lng":"",            "lat":"",         "region":"",        "waterQuality":""},
    {"name":"彩蓝桥镇","id":"20", "pId":0,  "open": "true",   "lng":"",            "lat":"",         "region":"",        "waterQuality":""},
    {"name":"丁向镇",  "id":"30", "pId":0,  "open": "true",   "lng":"",            "lat":"",         "region":"",        "waterQuality":""},
    {"name":"桃园东",  "id":"1",  "pId":10, "open":"",         "lng":"120.56934479","lat":31.85618831,"region":"向阳河",  "waterQuality":"I"},
    {"name":"董家桥村","id":"2",  "pId":10, "open":"",         "lng":"120.56709498","lat":31.90134260,"region":"向阳河",  "waterQuality":"II"},
    {"name":"庄上村",  "id":"3",  "pId":20, "open":"",         "lng":"120.55362585","lat":31.87984724,"region":"彩蓝桥河","waterQuality":"III"},
    {"name":"绣品街",  "id":"4",  "pId":20, "open":"",         "lng":"120.53118860","lat":31.86526444,"region":"彩蓝桥河","waterQuality":"IV"},
    {"name":"下村",    "id":"5",  "pId":30, "open":"",         "lng":"120.57111579","lat":31.85730531,"region":"丁向河",  "waterQuality":"V"}
];

解释：

// 创建对象
 let test = {name : 'lei'} // 获取对象的自身的属性
 test.name   //"lei"
 test["name"]   //"lei"
 // 获取不存在的属性
 test.age    //undefined
// 获取原型上的属性
 test["toString"]  //toString() { [native code] }
// 新增一个值为undefined的属性
test.un = undefined
test.un    //undefined 不能用在属性值存在，但可能为 undefined的场景