拷贝

深拷贝

function deepClone(obj) {
  const _toString = Object.prototype.toString

  // null, undefined, non-object, function
  if (!obj || typeof obj !== 'object') {
    return obj
  }

  // DOM Node
  if (obj.nodeType && 'cloneNode' in obj) {
    return obj.cloneNode(true)
  }

  // Date
  if (_toString.call(obj) === '[object Date]') {
    return new Date(obj.getTime())
  }

  // RegExp
  if (_toString.call(obj) === '[object RegExp]') {
    const flags = []
    if (obj.global) { flags.push('g') }
    if (obj.multiline) { flags.push('m') }
    if (obj.ignoreCase) { flags.push('i') }

    return new RegExp(obj.source, flags.join(''))
  }

  const result = Array.isArray(obj) ? [] : obj.constructor ? new obj.constructor() : {}

  for (const key in obj) {
    result[key] = deepClone(obj[key])
  }

  return result
}