rgbToHex.js

var convertNumberToHex = function( num ) {
  var hexDigits = ['0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'];
  var current = ['0','0'];
  var hexCounter = 1;
  var placeValue = 1;

  for ( var i = 1; i <= num; i++ ) {
    // if number is not at F
    if( hexCounter !== 16 ) {
      // replace it with the next highest
      current.pop();
      current.push( hexDigits[hexCounter] );
      hexCounter++;
      // if number is maxed out at F
    } else {
      // if it's not time to increase place values
      if( current[placeValue - 1] !== 'F' ) {
        hexCounter = 0;
        // increase the value of the digit previous to the PV we're changing
        current[placeValue - 1] = hexDigits[ hexDigits.indexOf( current[placeValue - 1] ) + 1 ];
        current.pop();
        current.push( hexDigits[hexCounter] );
        hexCounter++;
      } else {
        // Highest colors go is FF
        return 'FF';
      }
    }
  };

  return current.join('');
};

var rgb = function(n1, n2, n3) {
  var output = [];

  for (var i = 0; i < arguments.length; i++) {
    output.push( convertNumberToHex(arguments[i]) );
  };

  return output.join('');
};