The example you're talking about is just a pure JS usage, but this project recommends writing code in as3.
I say it can be used in big projects. First of all, he has most of the conditions for big projects. First, object oriented programming in the AS3 language, he can easily put other AS3 libraries into the project, such as I easily introduced box2d, tween. Second, flashdevelop, vscode, flashbuilder and other editors can be used for project development. Third, 80% flash API, introduced, such as loader, urllaoder, websocket,drawapi, mouseevent, displaylist, bitmap, stage3d, webglrenderer,etc., with these API, running a large project without any problems.