An addon for Datatables – adds a new row after row with index provided; based on Allan Jardine's code for fnAddTr (I kept his code and comments)

Datatables fnAddTrAfter

$.fn.dataTableExt.oApi.fnAddTrAfter = function ( oSettings, nTr, prevRowIdx, bRedraw ) {
    if ( typeof bRedraw == 'undefined' )
    {
        bRedraw = true;
    }
      
    var nTds = nTr.getElementsByTagName('td');
    if ( nTds.length != oSettings.aoColumns.length )
    {
        alert( 'Warning: not adding new TR - columns and TD elements must match' );
        return;
    }
      
    var aData = [];
    for ( var i=0 ; i<nTds.length ; i++ )
    {
        aData.push( nTds[i].innerHTML );

    }

    /* Add the data and then replace DataTable's generated TR with ours */
    var iIndex = this.oApi._fnAddData( oSettings, aData );
    nTr._DT_RowIndex = prevRowIdx+1;
    oSettings.aoData[ iIndex ].nTr = nTr;

  var tmpData = oSettings.aoData[iIndex];
	oSettings.aoData.splice(iIndex,1);
      	oSettings.aoData.splice(prevRowIdx+1,0,tmpData);

  /* If you don't need the correct indexes, I recommend removing this part 
    since it's slow */
	for (var i=prevRowIdx+2; i<oSettings.aoData.length; i++)
		oSettings.aoData[i].nTr._DT_RowIndex=i;

    oSettings.aiDisplay = oSettings.aiDisplayMaster.slice();
      
    if ( bRedraw )
    {
        this.oApi._fnReDraw( oSettings );
    }
};