Sort function to sort item numbers separated by colon
@Flambino was a bit faster : 

function sortSKU( a, b  )
{
    var aParts = a.split( ':' ),
        bParts = b.split( ':' ),
        partCount = aParts.length,
        i;

    if( aParts.length != bParts.length )
        return aParts.length - bParts.length;

    for( i = 0 ; i &lt; partCount ; i++ )
    {
      if( aParts[i] != bParts[i] )
        return +aParts[i] - +bParts[i];
    }
    //Exactly the same
    return 0;
}

console.log( data.sort( sortSKU )  );


As Flambino said, use .reverse() to sort one way or another. Also this function will sort 123 prior to 2:2 if such a case can occur.

If you need the 'c'

function sortingCallback( array, direction ){

  if( direction == 'whatever ascending is' ){
    return array.sort( sortSKU );
  }

  return array.sort( sortSKU ).reverse();
}