js 字符串转金额格式

function strMoney(str, n,strN) {
    let str1 = str.substring(0, str.length % n);
    let str2 = str.slice(2);
    let i = 0;
    let arrstr = [];
    while (i < str2.length) {
        arrstr.push(str2.slice(i, i + n));
        i += n;
    }
    let str3 = str1 + ',' + arrstr.join(',');
    let strn = str3.padStart(minN,'000,000,000');
    return strn;
}
console.log(strMoney('12345678', 3, 11));	//012,345,678

n为多少位为一段，str为原始字符串,strN为新字符串位数