javascript - 如果 key 名称未知，有没有办法访问 json 项目？

Question

我想从生成的 key (在 php 中生成并编码为 json)访问 json 项。是否可以增加变量来访问它？

这是我生成的 JSON(抱歉，这里看起来很奇怪):

{
"build1":{
  "object_id":1,
  "object_type":"school",
  "object_x":628,
  "object_y":131
  },
"build2":{
  "object_id":11,
  "object_type":"house",
  "object_x":631,
  "object_y":101
  },
"build3":{
  "object_id":12,
  "object_type":"school",
  "object_x":498,
  "object_y":131
  },
"build4":{
  "object_id":13,
  "object_type":"house",
  "object_x":770,
  "object_y":154
  },
"build5": {"object_id":14,
  "object_type":"house",
  "object_x":526,
  "object_y":217
  },
"build6":{
  "object_id":15,
  "object_type":"house",
  "object_x":563,
  "object_y":264
  }
} 

我尝试(糟糕地)用简单的技巧来做到这一点，但它不起作用。有办法吗？

这是我的代码:

for(var i=1; i<= buildingsLength; i++){

       var build= "build"+i;
       var buildaccess= "buildings"+"."+build;
       var buildType= buildaccess+"."+"object_type";

       if (buildType === "house"){
           console.log("yes, its a house");
           var img = new Image();
           img.src = "../img/house.png";
           img.onload = function(){
               ctx.drawImage(img,100,100);
           };
       }else if (buildType === "school") {
           console.log("yes, its a school");
           var img = new Image();
           img.src = "../img/school.png";
           img.onload = function(){
               ctx.drawImage(img,100,100);
           };
       }else{
           console.log("error");
       }
   }

我想访问“buildings.build1.object_type”，但“build1”应该以某种方式递增。

Answer 1

您可以使用Object.values()以数组形式获取对象的值。然后迭代它:

const myJson = {
"build1":{
  "object_id":1,
  "object_type":"school",
  "object_x":628,
  "object_y":131
  },
"build2":{
  "object_id":11,
  "object_type":"house",
  "object_x":631,
  "object_y":101
  },
"build3":{
  "object_id":12,
  "object_type":"school",
  "object_x":498,
  "object_y":131
  },
"build4":{
  "object_id":13,
  "object_type":"house",
  "object_x":770,
  "object_y":154
  },
"build5": {"object_id":14,
  "object_type":"house",
  "object_x":526,
  "object_y":217
  },
"build6":{
  "object_id":15,
  "object_type":"house",
  "object_x":563,
  "object_y":264
  }
};

for(let build of Object.values(myJson)){
   switch(build.object_type){
      case 'house':{
        console.log("It's a house!");
        break;
      }
      case 'school':{
        console.log("It's a school!");
        break;
      }
      default: break;
   }
}