If i delete and reinstall Minecraft will i still have the old worlds?

I tried to mod minecraft, but I ended up corrupting the jar file. If i reinstall it completely and log in with my account will I still have the old worlds?

Yes, If you just deleted minecraft launcher and not the minecraft folders where your saved worlds are

No you won't you will have to backup your saves folder onto a flashdrive or something (%appdata%>roaming>.minecraft>saves)