I deleted 1.8 in the versions folder and want to reinstall it. How does it work?
Minecraft Launcher → Edit Profile → Version → 1.8 → Save Profile → Play / Download.
However, I advise you to download version 1.8.8. This has some bug fixes and most mods work with it, unlike in 1.8.
If you have the premium launcher, you can always do it in launcher before starting the game
You start the launcher and go to the Profile tab.
→ Edit profile
→ Choose version
* 1.8.1 select *
→ Save.
Back to start and start with the corresponding profile. Then it will be downloaded.