Too Long; Didn't Read
The Elrond blockchain is a fully featured operational network, and you can build on it utilizing the fast and cheap chain. The smart contracts are written in Rust, and there is also an official JavaScript/Typescript SDK solution for all the interactions with the protocol and smart contracts, called erdjs. Excellent tool. You can interact with the protocol and custom smart contracts in the Node and browser. Yes, in the browser too, but there is one catch.