Developing frontend applications is not simple because crafting UI systems with a complex mutable state spread across the network is inherently difficult. This problem is still very new and thus does not have clear answers. At Grammarly, we have found the methodology that lets us tackle this complexity while keeping our codebase error-free and predictable. Our approach combines the pragmatic usage of functional programming with static typing. I will show you how functional programming can solve typical frontend problems effectively and elegantly.