Jump to a problem, path or page
Jump to a problem, path or page
Implementation lab
Edit JavaScript, run real behavioral tests in a sandboxed worker, and inspect the resulting state.
Define createParkingLot({ spots, charge, clock, price }) returning park, exit and snapshot. MOTORCYCLE fits MOTORCYCLE/CAR; CAR fits CAR; TRUCK fits TRUCK. charge returns CONFIRMED, FAILED or UNKNOWN; reuse the payment identity on retry. The starter passes 1/6; the worked solution 6/6.
1,593 / 40,000
Run → inspect → improve
Your next decision starts with evidence.
Run the starter to find its race and retry bugs. Fix one invariant, then run again.
Latest 30 runs, each with its exact inputs, results and notebook snapshot.
Run a second attempt to compare outcomes.
Engineering notebook