数字金额大写转换函数

const upDigit = n => {
    let fraction = ['角', '分','厘'];
    let digit = ['零', '壹', '贰', '叁', '肆', '伍', '陆', '柒', '捌', '玖'];
    let unit = [ ['元', '万', '亿'], ['', '拾', '佰', '仟']  ];
    let head = n < 0 ? '欠人民币': '人民币';
    n = Math.abs(n);
    let s = '';

    for( let i = 0; i < fraction.length; i++ ) {
        s += (digit[Math.floor(n * 10 * Math.pow(10, i)) % 10] + fraction[i]).replace(/零./, '');
    }
    s = s || '整';
    n = Math.floor(n);
    for( let i = 0; i < unit[0].length && n > 0; i++ ) {
        let p = '';
        for ( let j = 0; j < unit[1].length && n > 0; j++ ) {
            p = digit[n % 10] + unit[1][j] + p;
            n = Math.floor(n / 10);
        }
        s = p+ unit[0][i] + s;
    }
    return head + s.replace(/(零.)*零元/, '元').replace(/(零.)+/g, '零').replace(/^整$/, '零元整');
}