Converting from Base 10.

base_convert.js

var num = "27019",
    base = 16,
    output = '';

while (num > 0) {
  digit = num % base;
  num = (num - digit) / base;
  if (digit > 9) {
    digit = String.fromCharCode(digit + 55);
  }
  output = digit + output;
}

console.log(output);