function deepClone (obj) {

  if (obj === null) { // 如果是null则直接返回

    return obj;

  }

  let copy = Array.isArray(obj) ? [] : {};

  for (let key in obj) {

    if (obj.hasOwnProperty(key)) {

      if (typeof obj[key] === 'object') {

        copy[key] = deepClone(obj[key]);

      } else {

        copy[key] = obj[key];

      }

    }

  }

  console.log(copy);

  return copy;

}

let a = { name: '小明', age: 23, children: [1, { aa: 1 }, 2, 3], fn: function (v) { return v; } };

let b = deepClone(a);

console.log('b', b);