正则表达式实现字符串每4位后自动加空格效果(两种方法)

<input type="text" v-model="bankCard" @keyup="bankCardKeyup">bankCardKeyup (e) {  let self = this  // 如果是删除键，则不加空格，且删去字符串末端空格  if (e.keyCode === 8) {  self.bankCard = self.bankCard.replace(/[/s/n/t]+$/g, "")  return  }  self.bankCard = self.bankCard.replace(/[^0-9|' ']*/g, '')  let value = self.bankCard.replace(/[^0-9]*/g, '')  if (value.length > 4 && value.length <= 8) {  self.bankCard = value.slice(0, 4) + ' ' + value.slice(4, value.length)  }  else if (value.length > 8 && value.length <= 12) {  self.bankCard = value.slice(0, 4) + ' ' + value.slice(4, 8) + ' ' + value.slice(8, value.length)  }  else if (value.length > 12 && value.length <= 16) {  self.bankCard = value.slice(0, 4) + ' ' + value.slice(4, 8) + ' ' + value.slice(8, 12) + ' ' + value.slice(12, value.length)  if (value.length === 16) {   // 调用识别银行卡函数  }  }  else if (value.length > 16) {  self.bankCard = value.slice(0, 4) + ' ' + value.slice(4, 8) + ' ' + value.slice(8, 12)+ ' ' + value.slice(12, 16) + ' ' + value.slice(16, value.length)  if (value.length === 19) {   // 调用识别银行卡函数  }  else if (value.length > 19) {   self.bankCard = value.slice(0, 4) + ' ' + value.slice(4, 8) + ' ' + value.slice(8, 12)+ ' ' + value.slice(12, 16) + ' ' + value.slice(16, 19)  }  } },

<input type="text" v-model="bankCard" @keyup="bankCardKeyup">bankCardKeyup () { let self = this self.bankCard = self.bankCard.replace(//s/g,'').replace(/[^/d]/g,'').replace(/(/d{4})(?=/d)/g,'$1 ')}