深拷贝

深拷贝

function deepClone (obj, hash = new WeakMap()) {
  if (obj === null) return obj;
  if (obj instanceof Date) return new Date(obj);
  if (obj instanceof RegExp) return new RegExp(obj);
  if (typeof obj !== "object") return obj;

  if (hash.has(obj)) return hash.get(obj);

  // 这是克隆不是继承
  let cloneObj = new obj.constructor();
  hash.set(obj, cloneObj);

  for (let key in obj) {
    if (obj.hasOwnProperty(key)) {
      cloneObj[key] = deepClone(obj[key], hash);
    }
  }

  return cloneObj;
}