Get the player platform behavior

Is it possible to get the player platform behavior using javascript? I would like to setup all the things related "platform" using js.

First up, yes it is!

So the Behaviours are part of every instance object, so are fairly easy to access

The overall methods are documented here - construct.net/en/make-games/manuals/construct-3/scripting/scripting-reference/object-interfaces/iinstance

So an easy example would be

let myObj = runtime.objects.Player.getFirstInstance();

let platb = myObj.behaviors.Platform;