JavaScript is parsing the group of 3 numbers as an octal number when there's a leading zero digit. When the group of three digits is all zeros, the result is the same whether the base is octal or decimal.

But when you give JavaScript '009' (or '008'), that's an invalid octal number, so you get zero back.

If you had gone through the whole set of numbers from 190,000,001 to 190,000,010 you'd hav seen JavaScript skip '...,008' and '...,009' but emit 'eight' for '...,010'. That's the 'Eureka!' moment.

Change:

for (j = 0; j < finlOutPut.length; j++) {
    finlOutPut[j] = triConvert(parseInt(finlOutPut[j]));
}

to

for (j = 0; j < finlOutPut.length; j++) {
    finlOutPut[j] = triConvert(parseInt(finlOutPut[j],10));
}

Code also kept on adding commas after every non-zero group, so I played with it and found the right spot to add the comma.

Old:

for (b = finlOutPut.length - 1; b >= 0; b--) {
    if (finlOutPut[b] != "dontAddBigSufix") {
        finlOutPut[b] = finlOutPut[b] + bigNumArry[bigScalCntr] + ' , ';
        bigScalCntr++;
    }
    else {
        //replace the string at finlOP[b] from "dontAddBigSufix" to empty String.
        finlOutPut[b] = ' ';
        bigScalCntr++; //advance the counter  
    }
}

    //convert The output Arry to , more printable string 
    for(n = 0; n<finlOutPut.length; n++){
        output +=finlOutPut[n];
    }

New:

for (b = finlOutPut.length - 1; b >= 0; b--) {
    if (finlOutPut[b] != "dontAddBigSufix") {
        finlOutPut[b] = finlOutPut[b] + bigNumArry[bigScalCntr]; // <<<
        bigScalCntr++;
    }
    else {
        //replace the string at finlOP[b] from "dontAddBigSufix" to empty String.
        finlOutPut[b] = ' ';
        bigScalCntr++; //advance the counter  
    }
}

    //convert The output Arry to , more printable string 
    var nonzero = false; // <<<
    for(n = 0; n<finlOutPut.length; n++){
        if (finlOutPut[n] != ' ') { // <<<
            if (nonzero) output += ' , '; // <<<
            nonzero = true; // <<<
        } // <<<
        output +=finlOutPut[n];
    }