sequenceComps.jsx

(function() {
        function emptyDuplicate(comp, name) {
            return app.project.items.addComp(name, comp.width, comp.height, comp.pixelAspect, comp.duration, comp.frameRate);
        }

        function compByName(name) {
            for (var i = 1; i <= app.project.items.length; i++) {
                var item = app.project.items[i];
                if (item instanceof CompItem && item.name === name) {
                    return item;
                }
            }
        }

        function extendComp(comp) {

            // find and measure the longest AVItem contained in a layer
            var longestLayer = 0;
            var longestLength = 0

            for (var i = 1; i <= comp.layers.length; i++)
                if (comp.layers[i] instanceof AVLayer)
                        if (comp.layers[i].source.duration > longestLength)
                            {
                                longestLayer = i;
                                longestLength = comp.layers[i].source.duration;
                            }

            // extend all layers to match the duration of the longest AVItem
            for (var i = 1; i <= comp.layers.length; i++) comp.layers[i].outPoint = longestLength;

            // set the comp work area duration so that it lines up with the end of the longest footage
            comp.workAreaDuration = longestLength;

        }

        // get the name of the original comp supplied to nexrender
        var templateCompName = typeof _sequence !== 'undefined' && _sequence.get('template') || 'Comp 1';

        // get the template comp itself
        var templateComp = compByName(templateCompName);

        // make an emply duplicate with the same name as has been left with nexrender
        var comp = emptyDuplicate(templateComp, "__sequence__");

        // get the sequence of comps to create
        var sequenceParameters = typeof _sequence !== 'undefined' && _sequence.get('sequence') || [];

        // beginning at the top of the new empty comp
        var insertTime = 0;

        // for each comp referenced in the list
        for (var i = 0; i < sequenceParameters.length; i++) {

            if (sequenceParameters[i]['comp']) {

                // get it from the app
                var addComp = compByName(sequenceParameters[i]['comp']);

                // extend if required
                if (sequenceParameters[i]['extend']) extendComp(addComp)

                // add it 
                var newLayer = comp.layers.add(addComp);

                // and to the bottom of the stack
                newLayer.moveToEnd();

                //move it back if required to the current start point, accounting for the working area of the new comp
                newLayer.startTime = insertTime - addComp.workAreaStart;

                // trim the layer in point to the edit point
                newLayer.inPoint = insertTime;

                // trim the layer outpoint to the end of the new added comp work area
                newLayer.outPoint = insertTime + addComp.workAreaDuration;

                // remember where we ended
                insertTime = insertTime + addComp.workAreaDuration;

            }

        }

        // extend the new comp to fit in all the added layers
        comp.displayStartTime = 0;
        comp.duration = insertTime;
        comp.workAreaDuration = insertTime;

    })();