Functional Reactive Programming, or FRP for short, is a declarative style of UI design famous for ideas such as bidirectional data-bindings. This style of programming has been much popularized by frameworks such as React, which adapts many ideas from FRP.
There is an ambitious Web Framework in Rust called Yew that adapts many FRP concepts in a similar way to React. Throwing my hat into the ring I have made some declarative macros for simply generating HTML. Less or More, One way or Another, users tend to desire abstractions that behave in a declarative effective reactive intuitive manner. FRP embodies intuition in UI, striving against the naturally cascading deployment cycle that we are accustomed to as developers.