New Precomposer in AE CC function via script

Question

As we know new AE CC has got awesome checkbox called "Adjust composition duration to the time span of the selected layers".
Default setup in scripting guide is:
[object LayerCollection].precompose(array, string, [bool]);
But it doesn`t work with a new checkbox.
So how to operate with a new checkbox via script?
Thanks for reading.

Answer 1

I found that precomp function doesn`t work with app.project.activeItem.selectedLayers;
So here is the final touch that works with selected layers.
Cheers
function precompLayer() {
var myComp = app.project.activeItem;
if(myComp == null){alert("Please, select your composition"); return false;}
   var selectLayers = app.project.activeItem.selectedLayers; // выбранные
      if(selectLayers.length <1 ){alert("Please, select layers"); return false;}
   myLayers = [];      // precomp function works only with layers indexes, so array should contain layers indexes
        for (var l = 0; l< selectLayers.length; l++){
            myLayers.push(selectLayers[l].index);            // new array with layers indexes
var precompIndices = myLayers;  //change this to customize
        var precompName = "new_comp";  //change this to customize
        var parentComp = app.project.activeItem;  //change this to customize
        clearOutput();
        writeLn("Creating precompose");
        app.beginUndoGroup("Precompose");
        var Inpoint = 0;
        var Outpoint = 0;
        var precomp = parentComp.layers.precompose(precompIndices, precompName, true);    
        var adjustStartTime = precomp.duration, newCompDuration = 0;
        writeLn(precomp.layers.length+" layers in procompose");
        for(var i=1; i<=precomp.layers.length; i++) {
            var layer = precomp.layer(i);
            (Inpoint > layer.inPoint) ? Inpoint = layer.inPoint : Inpoint;                  // begin of precomp
            (Outpoint < layer.outPoint) ? Outpoint = layer.outPoint : Outpoint;       // end of precomp
            var duration = Outpoint - Inpoint;
            adjustStartTime = adjustStartTime > layer.inPoint ? layer.inPoint : adjustStartTime;
            newCompDuration = newCompDuration < duration? duration : newCompDuration;
            writeLn("New duration = "+newCompDuration);
        for(var i=1; i<=precomp.layers.length; i++) {
            precomp.layer(i).startTime -= adjustStartTime;
        precomp.duration = newCompDuration;
        parentComp.layer(precompName).startTime = adjustStartTime;
        app.endUndoGroup();
writeLn("Done!");
precompLayer();