深拷贝

实现

function deepClone(source) {
  if (typeof source !== "object" || source === null) {
    return source;
  }
  if (source instanceof Date) return new Date(source);
  if (source instanceof Set) return new Set(Array.from(source));
  if (source instanceof Map) return new Map(source.entries());

  const target = Array.isArray(source) ? [] : {};

  for (const key in source) {
    // 不克隆原型上的属性和方法
    if (Object.prototype.hasOwnProperty.call(source, key)) {
      // 解决循环引用问题
      if (source[key] === source) {
        target[key] = source;
      } else {
        target[key] = deepClone(source[key]);
      }
    }
  }

  return target;
}