duplicate_layer.jsx

/**
 * @author fabiantheblind
 * @description duplicates a layer 99 times
 *
 *
 * @todo [description]
 */
fun();
function fun(){


app.beginUndoGroup("XXX");

var curComp = app.project.activeItem;
   if (!curComp || !(curComp instanceof CompItem)){
        alert("noComp");
        return;
    }

var num = 99;

for(var i = 0; i < num; i ++){
        curComp.selectedLayers[0].duplicate();
    }

app.endUndoGroup();
}