Ethers.js
Ethers.js is a very popular JavaScript library for interacting with the Ethereum blockchain. You can create a Rivet-backed ethers.js provider using:
var ethers = require('ethers');
var provider = ethers.providers.JsonRpcProvider('https://YourApiKey.eth.rpc.rivet.cloud/');
From there, you can use the provider object as documented to pull data from Rivet.