javascript深度克隆

const mapTag = ‘[object Map]‘;
const setTag = ‘[object Set]‘;
const arrayTag = ‘[object Array]‘;
const objectTag = ‘[object Object]‘;
const argsTag = ‘[object Arguments]‘;
const boolTag = ‘[object Boolean]‘;
const dateTag = ‘[object Date]‘;
const numberTag = ‘[object Number]‘;
const stringTag = ‘[object String]‘;
const symbolTag = ‘[object Symbol]‘;
const errorTag = ‘[object Error]‘;
const regexpTag = ‘[object RegExp]‘;
const funcTag = ‘[object Function]‘;

const deepTag = [mapTag, setTag, arrayTag, objectTag, argsTag];

function forEach (array, iteratee) {
  let index = -1;
  const length = array.length;
  while (++index < length) {
    iteratee(array[index], index);
  }
  return array;
}

function isObject (target) {
  const type = typeof target;
  return target !== null && (type === ‘object‘ || type === ‘function‘);
}

function getType (target) {
  return Object.prototype.toString.call(target);
}

function getInit (target) {
  const Ctor = target.constructor;
  return new Ctor();
}

function cloneSymbol (targe) {
  return Object(Symbol.prototype.valueOf.call(targe));
}

function cloneReg (targe) {
  const reFlags = /\w*$/;
  const result = new targe.constructor(targe.source, reFlags.exec(targe));
  result.lastIndex = targe.lastIndex;
  return result;
}

function cloneFunction (func) {
  const bodyReg = /(\?<={)(.|\n)+(\?=})/m;
  const paramReg = /(\?<=\().+(\?=\)\s+{)/;
  const funcString = func.toString();
  if (func.prototype) {
    const param = paramReg.exec(funcString);
    const body = bodyReg.exec(funcString);
    if (body) {
      if (param) {
        const paramArr = param[0].split(‘,‘);
        return new Function(...paramArr, body[0]);
      } else {
        return new Function(body[0]);
      }
    } else {
      return null;
    }
  } else {
    return func.toString();
  }
}

function cloneOtherType (targe, type) {
  const Ctor = targe.constructor;
  switch (type) {
    case boolTag:
    case numberTag:
    case stringTag:
    case errorTag:
    case dateTag:
      return new Ctor(targe);
    case regexpTag:
      return cloneReg(targe);
    case symbolTag:
      return cloneSymbol(targe);
    case funcTag:
      return cloneFunction(targe);
    default:
      return null;
  }
}

export const clone = function (target, map = new WeakMap()) {
  // 克隆原始类型
  if (!isObject(target)) {
    return target;
  }

  // 初始化
  const type = getType(target);
  let cloneTarget;
  if (deepTag.includes(type)) {
    cloneTarget = getInit(target, type);
  } else {
    return cloneOtherType(target, type);
  }

  // 防止循环引用
  if (map.get(target)) {
    return map.get(target);
  }
  map.set(target, cloneTarget);

  // 克隆set
  if (type === setTag) {
    target.forEach(value => {
      cloneTarget.add(clone(value, map));
    });
    return cloneTarget;
  }

  // 克隆map
  if (type === mapTag) {
    target.forEach((value, key) => {
      cloneTarget.set(key, clone(value, map));
    });
    return cloneTarget;
  }

  // 克隆对象和数组
  const keys = type === arrayTag ? undefined : Object.keys(target);
  forEach(keys || target, (value, key) => {
    if (keys) {
      key = value;
    }
    cloneTarget[key] = clone(target[key], map);
  });
  return cloneTarget;
};