js格式化RMB

[21paradox]

const cnNums = ['零', '壹', '贰', '叁', '肆', '伍', '陆', '柒', '捌', '玖'];
const pos4OccurMap = {
  1: '',
  2: '万',
  3: '亿',
};
const Zero = '零';

function fmtNum(numStr) {
  let StrTxt = '';
  let pos4Occur = 0;

  const prependTxt = (a) => {
    StrTxt = a + StrTxt;
  };

  for (let indexFromLast = 0; indexFromLast < numStr.length; indexFromLast++) {
    const curIndex = numStr.length - 1 - indexFromLast;
    const curItem = numStr[curIndex];
    const pos4 = indexFromLast % 4;

    if (pos4 === 0) {
      pos4Occur += 1;
    }

    const fmtNormal = (name) => {
      const nextItem = numStr[numStr.length - indexFromLast];
      if (parseInt(curItem) === 0) {
        if (parseInt(nextItem) !== 0) {
          prependTxt(Zero);
        }
      } else {
        prependTxt(cnNums[curItem] + name);
      }
    };

    switch (pos4) {
      case 0: {
        if (curItem !== '0') {
          prependTxt(cnNums[curItem] + pos4OccurMap[pos4Occur]);
        } else if (
          numStr[curIndex] === '0'
            && numStr[curIndex - 1] === '0'
            && numStr[curIndex - 2] === '0'
            && numStr[curIndex - 3] === '0'
        ) {
          if (typeof numStr[curIndex + 1] !== 'undefined' && numStr[curIndex + 1] !== '0') {
            prependTxt(Zero);
          }
        } else {
          prependTxt(pos4OccurMap[pos4Occur]);
        }
        break;
      }
      case 1: {
        fmtNormal('拾');
        break;
      }
      case 2: {
        fmtNormal('佰');
        break;
      }
      case 3: {
        fmtNormal('仟');
        break;
      }
      default:
        break;
    }
  }
  return StrTxt;
}

function fmtDecimal(numStr, showZero) {
  if (numStr.length === 0) {
    return '';
  }
  if (numStr.length === 1) {
    return `${cnNums[numStr[0]]}角`;
  }

  let desTxt = '';
  if (numStr[0] === '0') {
    if (showZero === true) {
      desTxt += Zero;
    }
  } else {
    desTxt += `${cnNums[numStr[0]]}角`;
  }
  if (numStr[1] !== '0') {
    desTxt += cnNums[numStr[1]];
    desTxt += '分';
  }
  return desTxt;
}

function toRmb(a) {
  const [partInt = '', partDes = ''] = a.split('.');
  if (parseInt(partInt, 10) === 0 && parseInt(partDes, 10) === 0) {
    return '零元整';
  }
  if (partInt === '0' && partDes) {
    return fmtDecimal(partDes, false);
  }
  if (!partDes || parseInt(partDes, 10) === 0) {
    return `${fmtNum(partInt)}元整`;
  }
  return `${fmtNum(partInt)}元${fmtDecimal(partDes, true)}`;
}

module.exports = toRmb;