Hexadecimal to RGB conversion

I am trying to convert hex to rgb, and rgb to hex. My current code doesn't seem optimal, and there is an issue with 0's in the hexadecimal. What do you think about the overall quality of this code? Can you think of a more efficient way of converting?

$scope.$watch('hex', function() {
    var rgb = parseInt($scope.hex, 16);
    $scope.r = (rgb >> 16) & 0xFF;
    $scope.g = (rgb >> 8) & 0xFF;
    $scope.b = rgb & 0xFF;
    $scope.rgb = 'rgb(' + $scope.r + ',' + $scope.g + ',' + $scope.b + ');';
  });

  $scope.$watch('r+g+b', function() {
    $scope.rgb = 'rgb(' + $scope.r + ',' + $scope.g + ',' + $scope.b + ');';
    $scope.hex = parseInt($scope.r << 16 | $scope.g << 8 | $scope.b).toString(16);
  });

Here is a sample plunker:

A few notes:

-
I am confused as to why you need AngularJS for this.

-
I prefer to use the bitwise & with 255 instead of 0xFF in this case.

-
Your function can't handle non-hex characters such as #. I would remove them before parsing.

-
You can simplify your creation of the RGB string by using the join() method.

Final function:

function hexToRgb(hex) {
    hex = hex.replace(/[^0-9A-F]/gi, '');
    var bigint = parseInt(hex, 16);
    var r = (bigint >> 16) & 255;
    var g = (bigint >> 8) & 255;
    var b = bigint & 255;

    return [r, g, b].join();
}

StackExchange Code Review Q#60515, answer score: 11