金额小写转大写

// val是金额可以是数字/字符串 len是小数点后几位，默认2位
const formatUpper = (val, len = 2) => {
  let n = val.toString();
  const flagLen = typeof len !== 'number' || (typeof len === 'number' && (len < 0 || len > 6));
  if (!val) {
    return;
  }
  if (!/^(0|[1-9]\d*)(\.\d+)?$/.test(n) || flagLen) {
    return '数据非法';
  }
  let unit: string = '千百拾亿千百拾万千百拾元角分厘毫微纳皮';
  let str: string = '';
  const p: number = n.indexOf('.');
  n += '0'.repeat(len);
  const unitFrac: number = unit.slice(unit.indexOf('元') + 1).length;
  if (p >= 0) {
    n = n.substring(0, p) + n.substr(p + 1, len);
    unit = unit.substr(len - unitFrac - n.length, n.length);
  } else {
    unit = unit.substr(len - unitFrac - n.length, n.length + len);
  }
  for (var i = 0; i < n.length; i++) {
    str += '零壹贰叁肆伍陆柒捌玖'.charAt(n.charAt(i)) + unit.charAt(i);
  }
  return str
    .replace(/零(千|百|拾)/g, '零')
    .replace(/(零)+/g, '零')
    .replace(/零(万|亿|元)/g, '$1')
    .replace(/(亿)万|壹(拾)/g, '$1$2')
    .replace(/^元零?|零角|零分|零厘|零毫|零微|零纳|零皮/g, '')
    .replace(/元$/g, '元整');
};