js 数字转英文（笔试遇到过两次

//数字转英文
const arr1 = ["zero","one","two","three","four","five","six","seven","eight","nine"],
    arr2 = ["ten","eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","nineteen"],
    arr3 = ["tewnty","thirty","forty","fifty","sixty","seventy","eighty","ninety"],
    arr4 = ["hundred","thousand","million","billion","trillion","quadrillion"];

function doubledight(n){
    var result = "";
    if(parseInt(n)!=0){
        var dd = n.split('');
        if(dd[0]<1){
            result = arr1[dd[1]];
        }else if(dd[0]==1){
            result = arr2[dd[1]];
        }else{
            result = arr3[dd[0]-2] + "-" + arr1[dd[1]];
        }
    }
    return result;
}

function num2Eng(s){
    s = s.split('');
    while(s.indexOf('0')===0){
        s.shift();
    }
    s = s.join('');
    var res = '';
    while(s.length>3){
        res = ',' + s.slice(-3) + res;
        s = s.slice(0,s.length-3);
    }
    if(s){
        res = s + res;
    }

    var fenge = res.split(',');
    var result = "";
    for(let i=0;i<fenge.length;i++){
        if(fenge[i].length === 3){
            result += arr1[fenge[i].substring(0,1)]+" ";//百位
            result += arr4[0];
            if(doubledight(fenge[i].substring(1))!=""){
                result += " and " + doubledight(fenge[i].substring(1));
            }
        }else if(fenge[i].length ==2){
            result +=doubledight(fenge[i]);
        }else if(fenge[i].length == 1){
            result += arr1[fenge[i]];
        }
        if(i<fenge.length -1){
            result += " " +arr4[fenge.length-1-i] + " ";
        }
    }
    return result;
}
var s1 = '2356';
console.log(num2Eng(s1));
var s2 = '9875538376';
console.log(num2Eng(s2));
var s3 = '00000002356';
console.log(num2Eng(s3));