deep clone

clone.js

function deepClone() {
  let copy

  // 处理3个简单的类型, null 或者 undefined
  if (obj === null || typeof obj !== 'object') {
    return obj
  }

  if (obj instanceof Date) {
    copy = new Date()
    copy.setTime(obj.getTime())
    return copy
  }

  if (obj instanceof Array) {
    copy = []
    for (var i = 0, len = obj.length; i < len; i++) {
      copy[i] = clone(obj[i])
    }
    return copy
  }

  if (obj instanceof Object) {
    copy = {};
    for (var attr in obj) {
      if (obj.hasOwnProperty(attr)) {
        copy[attr] = clone(obj[attr])
      }
    }
    return copy
  }

  throw new Error("Unable to copy obj! Its type isn't supported.")
}