Used for class rooms, Only uses this format: 1 or 2 digits first and 1 letter optional

addZeroToFront.js

//Used for class rooms
//Only uses this format: 1 or 2 digits first and 1 letter optional
//input examples: "2k", "20k", "1", "10"
//output examples:"02k","20k", "01", "10"

function addZeroToFront(nr) {
                var val = nr;
                var numbers = Number(val.replace(/[a-zA-Z]/g, ''));
                var letter = val.replace(/[0-9]/g, '');
                if (val !== "") {
                    var letter = val.replace(/[0-9]/g, '');
                    var numbers = Number(val.replace(/[a-zA-Z]/g, ''));
                    if (numbers.toString().length === 1 && val !== 0) {
                        return "0" + numbers + letter;
                    }
                }
                return val
            }