json如下：

var json = 
{
    city: "浙江省/宁波市",
    code: 200,
    data: {
    ljjf: "0"
    },
    initurl: "https://ngb.122.gov.cn/views/inquiry.html",
    message: "操作成功！"
}
 

代码如下：

if(json.hasOwnProperty("city")){
    console.log(json["city]);
}