javascript - 如何创建一个内部有数组的动态对象，使其不会被覆盖？

Question

如何创建一个内部有数组的动态对象，使其不会被覆盖？

    let id;
    let obj = {};
    obj[id] = []; // if I declare  here inside the function it is undefined

    function ex(event) {
       id = event.id;
       obj[id] = [];// if I declare obj[id]=[]  here its overwrite
       obj[id].push(event.data);
    }

    //what needs to be done to get global obj like this


     {
         31dsa: ['sdf32da', '3fsdffs'],
         1dfga: ['hfs32da'],
         ....
    }

Answer 1

您可以验证数组是否存在。

 function ex(event) {
   id = event.id;
   if (!obj[id]){ // if undefined its falsy
      obj[id]= [];
   }
   obj[id].push(event.data);
}