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Manuals / TypeScript / Checkpoint 5

B · Modeling · intermediate · Gate · Week 2–3 · Checkpoint 5 of 11

Checkpoint A — Strict types & unions

Before generics and utilities, prove strict setup works and you can model real states with unions. Fix gaps before Phase C.

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Step 1 of 2

Pass criteria

  • tsconfig strict: true, npm run typecheck script works
  • Core utils converted to .ts with typed params and returns
  • Domain models (User, Post, etc.) in types/models.ts
  • FetchState or Result discriminated union in use
  • Zero any (or each any has // ponytail: escape hatch comment)
  • Can explain type vs interface in one sentence
Pass criteriaDrag stickies · tap for tips
Study mapDrag stickies · tap for tipsKeep it shortdrag · tap →Name the waitdrag · tap →Scope locatorsdrag · tap →Trace when stuckdrag · tap →One browser firstdrag · tap →Isolate statedrag · tap →Assert the UIdrag · tap →Retry wiselydrag · tap →Seed datadrag · tap →Close the loopdrag · tap →Keep it shortdrag · tap →Name the waitdrag · tap →Scope locatorsdrag · tap →Trace when stuckdrag · tap →One browser firstdrag · tap →Isolate statedrag · tap →Pathwise hackdrag · tap →Pass criteriadrag · tap →Try thisdrag · tap →Follow the dashed drag · tap →

Do this now

Audit each criterion. Fix failures before continuing.

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Chapter learning outcomes
  • Type safety self-check

Clear these before you leave

Side quest

Typecheck green

npm run typecheck && npm run test:run both green on your project.