Simplest Explanation

Get all of the layers in a timeline

By using JSFL, you can use this code to get a list of all of the layers in a timeline. This is returned as an array of named objects whose data is accessible like this:

var layers = getLayers(fl.getDocumentDOM().getTimeline());
layers[0].name

This will return the first layer’s name.

var getLayers = function(timeline){
   var layers = [];
   for(var l in timeline.layers){
      layers.push({
         name:timeline.layers[l].name,
         layer:timeline.layers[l],
         index:l
      });
   }
   return layers;
};

Get all of the keyframes in a layer

By using JSFL, you can use this code to get a list of all of the Keyframes on a layer. This is returned as an array of named objects whose data is accessible like this:

var keyframes = getKeyframes(fl.getDocumentDOM().getTimeline().layers[0]);
keyframes[0].index;

This will return the first keyframe’s index, allowing you to reference it later using layer.frames[index].

var getKeyframes = function(layer){
   var keyframes = [];
   for(var f in layer.frames){
      if (f==layer.frames[f].startFrame){
         keyframes.push({
            frame:layer.frames[f],
            index:f
         });
      }
   }
   return keyframes;
};

Get all of the instances in a keyframe

By using JSFL, you can use this code to get a list of all of the instances on a keyframe. This is returned as an array of named objects whose data is accessible like this:

var instances = getInstances(fl.getDocumentDOM().getTimeline().layers[0].frames[0]);
instances[0].index;

This will return the first instance’s index, allowing you to reference it later using frame.instances[index].

var getInstances = function(keyframe){
   var instances = [];
   for(var e in keyframe.elements){
      if(keyframe.elements[e].elementType == 'instance'){
         if(keyframe.elements[e].libraryItem.itemType != 'compiled clip'){
            instances.push({
               instance:keyframe.elements[e], 
               index:e
            });
         }
      }
   }
   return instances;
};