【AE脚本】基于选择顺序 把图层首尾相连

/*
written for this stackoverflow question
http://stackoverflow.com/questions/24115505/after-effects-composition-start-time-on-timeline/24117772#24117772
*/
function fun() {
  app.beginUndoGroup('XXX');
  var curComp = app.project.activeItem;
  if (!curComp || !(curComp instanceof CompItem)) {
    alert('选个合成行不行');
    return;
  }
  selLayers = curComp.selectedLayers
  if(selLayers.length < 3) {
    alert('多选点图层行不行');
    return;
  }

  for (var i = 1; i < selLayers.length; i++) {
    selLayers[i].startTime = selLayers[i-1].outPoint  - (selLayers[i].inPoint - selLayers[i].startTime);
}
  app.endUndoGroup();

}

fun();