code: function replaceCssLength( length1, length2 ) {
  		var parts1 = cssLengthRegex.exec( length1 ),
  			parts2 = cssLengthRegex.exec( length2 );
  
  		// Omit pixel length unit when necessary,
  		// e.g. replaceCssLength( 10, '20px' ) -> 20
  		if ( parts1 ) {
  			if ( !parts1[ 2 ] && parts2[ 2 ] == 'px' )
  				return parts2[ 1 ];
  			if ( parts1[ 2 ] == 'px' && !parts2[ 2 ] )
  				return parts2[ 1 ] + 'px';
  		}
  
  		return length2;
  	}
docs: Replacing the former CSS length value with the later one, with adjustment to the length  unit.