Javascript function to format currency

Question

I am using the below function to generate formatted comma separated currency value in javascript but its not working for certain scenarios:

1234 => 1,234 (correct)
1.03 => 1.3 (wrong)

how can i fix the issue in my below function:

function formatThousands(n, dp) {
    var s = '' + (Math.floor(n)), d = n % 1, i = s.length, r = '';
    while ((i -= 3) > 0) { 
        r = ',' + s.substr(i, 3) + r; 
    }
    return s.substr(0, i + 3) + r + (d ? '.' + Math.round(d * Math.pow(10, dp || 2)) : '');
}

Thanks in advance

Answer 1

To fix your code we need to make sure the rest has at least as much digits as the "dp" parameter, if not we will add leading zeros.

function formatThousands(n, dp) {
    var s = '' + (Math.floor(n)), d = n % 1, i = s.length, r = '';
    while ((i -= 3) > 0) { 
        r = ',' + s.substr(i, 3) + r; 
    }
    var rest = Math.round(d * Math.pow(10, dp || 2));
    var rest_len = rest.toString().length;
    if(rest_len < dp) {
        rest = '0'.repeat(dp - rest_len) + rest;
    }
    return s.substr(0, i + 3) + r + (rest ? '.' + rest : '');
}
console.log(formatThousands(1234.14, 2));       //1,234.14
console.log(formatThousands(1.003526, 4));      //1.0035

Anyway you could definitely find cleaner version of thousands separation as others mentioned in comments.