Ionic Directory Folder and file

Why all the tutorials I get, using app.js as a controller? while in ionic 3 that i install, when not find app.js file

is there anybody can help me explain about ionic folder structure?

app.component.js is there ?

every time build new project, directory always same. and i not found app.js

in which tutorial you found app.js used as controller ?
because if you are develop app in ionic ,it must be .ts file as controller.

Angular 4 Tutorial

Did you try this tutorial? It’s not specific for Ionic, but for Angular, what it’s based on… I think this should give you a first good Impression.