Where to add raycasting function and code?

[meet1919]

Hello, I have followed the Discover Three JS book so far. I want to use Raycaster in my code to add tooltip on object hover. But the code structure in the book seems complicated. The structure has different files for components (camera.js, light.js, cube.js, etc), system (renderer.js, controls.js, loop.js) and a World.js.

On the tutorials I found online aboyt Raycasting, the code in that tutorials have a single file containing everything (scene, camera, render) so it seems logocal to add code of raycasting in a single file. But it gets complicated to put the code in the structure describe in Discover Three JS. Can anyone help me where to add the code: component, system or World.js?