.定义公共方法，新建一个js文件checkBank.js

const checkBank = function luhmCheck (bankno) {
  let lastNum = bankno.substr(bankno.length - 1, 1) // 取出最后一位（与luhm进行比较）
  let first15Num = bankno.substr(0, bankno.length - 1) // 前15或18位
  let newArr = []
  for (let i = first15Num.length - 1; i > -1; i--) { // 前15或18位倒序存进数组
    newArr.push(first15Num.substr(i, 1))
  }
  let arrJiShu = [] // 奇数位*2的积 < 9
  let arrJiShu2 = [] // 奇数位*2的积 >9

  let arrOuShu = [] // 偶数位数组
  for (let j = 0; j < newArr.length; j++) {
    if ((j + 1) % 2 === 1) { // 奇数位
      if (parseInt(newArr[j]) * 2 < 9) {
        arrJiShu.push(parseInt(newArr[j]) * 2)
      } else {
        arrJiShu2.push(parseInt(newArr[j]) * 2)
      }
    } else {
      arrOuShu.push(newArr[j])
    }// 偶数位
  }
  let jishuChild1 = [] // 奇数位*2 >9 的分割之后的数组个位数
  let jishuChild2 = [] // 奇数位*2 >9 的分割之后的数组十位数
  for (let h = 0; h < arrJiShu2.length; h++) {
    jishuChild1.push(parseInt(arrJiShu2[h]) % 10)
    jishuChild2.push(parseInt(arrJiShu2[h]) / 10)
  }
  let sumJiShu = 0 // 奇数位*2 < 9 的数组之和
  let sumOuShu = 0 // 偶数位数组之和
  let sumJiShuChild1 = 0 // 奇数位*2 >9 的分割之后的数组个位数之和
  let sumJiShuChild2 = 0 // 奇数位*2 >9 的分割之后的数组十位数之和
  let sumTotal = 0
  console.log(sumTotal)
  for (let m = 0; m < arrJiShu.length; m++) {
    sumJiShu = sumJiShu + parseInt(arrJiShu[m])
  }
  for (let n = 0; n < arrOuShu.length; n++) {
    sumOuShu = sumOuShu + parseInt(arrOuShu[n])
  }
  for (let p = 0; p < jishuChild1.length; p++) {
    sumJiShuChild1 = sumJiShuChild1 + parseInt(jishuChild1[p])
    sumJiShuChild2 = sumJiShuChild2 + parseInt(jishuChild2[p])
  }
  // 计算总和
  sumTotal = parseInt(sumJiShu) + parseInt(sumOuShu) + parseInt(sumJiShuChild1) + parseInt(sumJiShuChild2)
  // 计算Luhm值
  let k = parseInt(sumTotal) % 10 === 0 ? 10 : parseInt(sumTotal) % 10
  let luhm = 10 - k
  if (Number(lastNum) === luhm && lastNum.length !== 0 && bankno.length > 11) {
    return true
  } else {
    return false
  }
}
export default checkBank