深拷贝的简单实现

[tag]:记录|js|deep copy
[create]:2019-10-25

const _toString = Object.prototype.toString;

function _isObject(val) {
  return _toString.call(val) === '[object Object]';
}

function _isArray(val) {
  return _toString.call(val) === '[object Array]';
}

function _forEach(val, fn) {
  if (val === null || typeof val === 'undefined') {
    return;
  }
  // 对象与数组选用不同的循环方式，因为for in循环性能比较不好
  if (_isArray(val)) {
    for (let i = 0; i < val.length; i++) {
      fn && fn(val[i], i);
    }
  } else if (_isObject(val)) {
    for (let key in val) {
      fn && fn(val[key], key);
    }
  } else {
    fn && fn(val, 0);
  }
}

function deepCopy(newObj, copyObj) {
  _forEach(copyObj, function(val, key) {
    if (_isObject(val)) {
      newObj[key] = deepCopy({}, val);
    } else if (_isArray(val)) {
      newObj[key] = deepCopy([], val);
    } else {
      newObj[key] = val;
    }
  });
  return newObj;
}