How to create a level checker in JS?

I’m facing a problem, let me explain :

  • I have 20 levels
  • I have users ( id )

I need to check which level is the user. How I do that in my use case :

  • I get the ID of the user and I need to check which level he has in order to assign him a special discount.

I can do 20 if(level1.include(id))... but that’s not clean, how could I do that in a better way ?