1. // 递归
    2. function dfsCloneDeep(source, hash = new WeakMap()) {
    3.     if (!typeof sorce === 'object') return source; // 非对象返回自身
    4.     if (hash.has(source)) return hash.get(source); // 查哈希表,如果以拷贝，则直接返回值，解决循环引用
    6.     let target = Array.isArray(source) ? [] : {}; // 区分数组和对象
    7.     hash.set(source, target); // 哈希表设值，哈希表存储已拷贝过的对象
    9.     let symKeys = Object.getOwnPropertySymbols(source); // 解决拷贝symbol
    10.     if (symKeys.length) {
    11.         symKeys.forEach(symKey => {
    12.             if (typeof source[symKey] === 'object' && source[symKey] !== null) {
    13.                 target[symKey] = dfsCloneDeep(source[symKey], hash); 
    14.             } else {
    15.                 target[symKey] = source[symKey];
    16.             }    
    17.         });
    18.     }
    20.     for(let key in source) {
    21.         if (Object.prototype.hasOwnProperty.call(source, key)) {
    22.             if (typeof source[key] === 'object' && source[key] !== null) {
    23.                 target[key] = dfsCloneDeep(source[key], hash); // 注意这里传入hash
    24.             } else {
    25.                 target[key] = source[key];
    26.             }
    27.         }
    28.     }
    29.     return target;
    30. }
    31. // 队列
    32.  function bfsCloneDeep(obj) {
    33.    let root = Array.isArray(obj) ? [] : {};
    34.    let nodeList = [{
    35.        parent: root,
    36.        key: undefined,
    37.        data: obj,
    38.    }];
    39.    while (nodeList.length) {
    40.      let node = nodeList.pop(),
    41.          parent = node.parent,
    42.          key = node.key,
    43.          data = node.data;
    44.      let result = parent;
    45.      if (typeof key !== 'undefined') { // 初始化赋值目标，key为undefined则拷贝到父元素，否则拷贝到子元素
    46.         result = parent[key] = Array.isArray(data) ? [] : {};
    47.      }
    49.      let symKeys = Object.getOwnPropertySymbols(data); // 解决拷贝symbol
    50.      if (symKeys.length) {
    51.           symKeys.forEach(symKey => {
    52.             if (typeof data[symKey] === 'object' && data[symKey] !== null) {
    53.                 nodeList.push({
    54.                    parent: result,
    55.                    key: symKeys,
    56.                    data: data[symKey],
    57.                 });
    58.             } else {
    59.               result[symKey] = data[symKey];
    60.             }
    61.          });
    62.       }
    64.       for (let key in data) {
    65.           if (data.hasOwnProperty(key)) {
    66.              if (typeof data[key] === 'object') {
    67.                  nodeList.push({
    68.                     parent: result,
    69.                     key,
    70.                     data: data[key],
    71.                  });
    72.              } else {
    73.                  result[key] = data[key];
    74.              }
    75.           }
    76.        }
    77.     }
    78.     return root;
    79. };
    80. let obj = {colors: ['blue', 'red'],width: 200, height: 300};
    81. let l = Symbol('length');
    82. obj[l] = 400 ;
    83. let obj1 = bfsCloneDeep(obj)
    84. // {colors: ['blue', 'red'], width: 200, height: 300, Symbol(length): 400}
    85. let obj2 = dfsCloneDeep(obj)
    86. // {colors: ['blue', 'red'], width: 200, height: 300, Symbol(length): 400}