150Build an interactive coding playground with sandboxing, test execution, worker-based timeouts, and persisted solutions

Build the engine behind a coding-practice editor (like the one on this page): run a learner's code against a test suite safely, quickly and offline.

createPlayground({ storage, timeout = 2000 }) returns:

• run(code, tests): execute code and then tests in a fresh, isolated Web Worker, and resolve with { results, logs }:
  • inside the worker, provide test(name, fn) (sync or async functions) and expect(value) with toBe, toEqual (deep equality) and toThrow(message?);
  • tests run in order; each result is { name, passed, error? } (the assertion message for failures);
  • console.log lines are captured in logs;
  • if the code itself throws (or has a syntax error), resolve with { results: [], logs, error };
  • remove fetch, XMLHttpRequest, WebSocket and importScripts before running;
  • if the whole run exceeds timeout ms (an infinite loop in code or a test), terminate the worker and reject with an error named "TimeoutError".
• save(questionId, code) and load(questionId, fallback): persist each question's latest code as { code, savedAt } JSON under "playground:{questionId}" in storage (getItem/setItem). load returns fallback for missing or corrupt data.