E · Deep JSAdvanced40 min read
12. Checkpoint B — Async, modules & tests
JavaScript · 56 pages source format
Prove you can ship a modular async app with tests and explain the event loop. This is the bar for "I know JavaScript" on a resume or in a QA automation interview.
What you'll learn
- Integration readiness
- Interview prep
Pass criteria
- Vite project with api/render/main module split
- Fetch app with loading, success, error, retry states
- 10+ Vitest tests, all green via npm run test:run
- Can explain event loop order (sync → microtasks → macrotask) without notes
- Can explain closure with createCounter example
- GitHub repo with README, meaningful commit history
Do this now
Verify every item. Fix gaps this week.
Clear?
Mock interview
Practice aloud: "What happens when you await fetch?" "Difference between == and ===?" "What is event delegation?"
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Record 5-minute answers to those three questions. Re-record until smooth.
Clear?
Code quality pass
Run ESLint if configured. Remove console.logs except intentional ones. Ensure no hardcoded URLs without env var.
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Final polish commit: "chore: checkpoint B ready".
Clear?