对象深拷贝

1.通过递归函数
  function deepCopy(obj) {
        let newObj = Array.isArray(obj) ? [] : {};
        for (var key in obj) {
          // 判断是否是数组类型
          if (obj[key] instanceof Array) {
            newObj[key] = [];
            deepCopy(obj[key]);
          } else if (obj[key] instanceof Object) {
            newObj[key] = {};
            deepCopy(obj[key]);
          } else {
            newObj[key] = obj[key];
          }
          return newObj;
        }
  }

2.通过MessageChannel()构造函数
function deepClone(obj){
  return new Promise((resolve)=>{
    const { port1, port2 } = new MessageChannel()
    port1.postMessage(obj)
    port2.onmessage =  msg =>{
       resolve(msg.data)
   }
})
}
let obj ={a:1,b:2}
obj.c = obj
deepClone(obj).then((res)=>{
  console.log(res)
})