Every lab ships a working front end that calls one harmless route. The route worth finding is in the bundle too - behind a rotated string array, an orphan chunk, an XOR table, a client-side signer or an RC4-packed second stage. Difficulty climbs from lab 1 to lab 5.
Tooling that helps: DevTools Sources + Console, de4js / obfuscator.io deobfuscators, JS Beautify, LinkFinder, curl for the final request.