SOURCE

function snowId(type) {
  let id = ''
  let idEx = ''
  let len = 4
  switch (type) {
    case 'building':
      idEx = 'BD'
      len = 4
      break
    case 'user':
      idEx = 'US'
      len = 6
      break
    case 'order':
      idEx = 'OD'
      len = 10
      break
    default:
      break
  }
  let timeStampSuffix = ''
  // id = 前缀 + 时间戳后缀
  let timeStamp = new Date().getTime().toString()
  timeStampSuffix = timeStamp.slice(timeStamp.length-1-len, timeStamp.length-1)
  id = idEx + timeStampSuffix
  return id
}
console.log(snowId('building'))
console.log(snowId('user'))
console.log(snowId('order'))