Grouper Script

app.beginUndoGroup("Grouper");

var activeItem = app.project.activeItem;

var xmin;
var xmax;
var ymin;
var ymax;

//If focus is on Layers
if ((activeItem != null) && (activeItem instanceof CompItem)){

        selectedLayers = activeItem.selectedLayers;

        if(selectedLayers.length>0) {

            minIndex = selectedLayers[0].index;
            xmin = xmax =  selectedLayers[0].property("Position").value[0];
            ymin = ymax =  selectedLayers[0].property("Position").value[1];

            activeItem.layers.addNull();
            var newNull = activeItem.layer(1);
            newNull.name = "Group Null";

            var ctr= 0;
            var minIndex;

            for each (lay in selectedLayers){
                    ctr++;
                    minmaxX( lay.property("Position").value[0] );
                    minmaxY( lay.property("Position").value[1] );
            }
            xpos = ((xmax-xmin)/2)+xmin;
            ypos = ((ymax-ymin)/2)+ymin;
            newNull.property("Position").setValue([xpos,ypos]);

            for each (lay in selectedLayers){
                    lay.parent = newNull;
                    if(lay.index<minIndex){minIndex = lay.index;}
            }
            myLay = activeItem.layers[minIndex]
            if(myLay.index>1){newNull.moveAfter(myLay);}
        }
}

// If focus is on Project Window
else {
        var mySelectedItems = [];
        for (var i = 1; i <= app.project.numItems; i++){
          if (app.project.item(i).selected)
            mySelectedItems[mySelectedItems.length] = app.project.item(i);
        }

        var myFolder = app.project.items.addFolder("Untitled Group");

        var tempFolder = mySelectedItems[0].parentFolder;
        var sameFolder = true;

        for each(item in mySelectedItems){
            if(item.parentFolder!=tempFolder){sameFolder = false;}
        }

        if(sameFolder){
            for each(item in mySelectedItems){
                item.parentFolder = myFolder;item.selected=false;
            }
            myFolder.parentFolder = tempFolder;
        } else {
            for each(item in mySelectedItems){
                item.parentFolder = myFolder;item.selected=false;
            }
        }
        myFolder.selected=true;
}

// Placement functions
function minmaxX(xIn){
        if(xIn>xmax){ xmax = xIn; }
        if(xIn<xmin){ xmin = xIn; }
}

function minmaxY(yIn){
        if(yIn>ymax){ ymax = yIn; }
        if(yIn<ymin){ ymin = yIn; }
}