拷贝一个对象（修改新对象不改变原对象）

export const cloneObject = (obj) => {
  let newObj = {}
  if (obj instanceof Array) {
    newObj = []
  }
  for (var key in obj) {
    let val = obj[key]
    if (val === null) {
      newObj[key] = null
    } else {
      newObj[key] = typeof val === 'object' ? cloneObject(val) : val
    }
  }
  return newObj
}