TypeScript Code Doctor

TypeScript Code Doctor: practical plan

Safer API boundary

A TypeScript interface is erased at runtime, so response.json() as User does not validate untrusted data. Parse the response as unknown, validate required fields and constraints, then return a typed value or a structured error.

Design

Define a runtime schema for ID, display name, account state and optional fields. Reject invalid enum values and unexpected nulls according to the API contract. Keep transport errors distinct from validation errors.

Tests

• Valid minimal and full payloads
• Missing required field
• Wrong primitive type
• Null where not allowed
• Unknown enum value
• Extra fields and forward-compatible additions
• Non-2xx response and malformed JSON

Type design

Prefer discriminated unions for account states and avoid broad any. Use unknown at external boundaries and derive types from the schema when practical.

Rollout

Add validation telemetry without logging personal payloads. Track rejection rates and coordinate contract changes with the API owner. Keep a compatibility policy for additive fields and versioned breaking changes.

Measurement and review

Record the baseline, source, date range, denominator and owner. Use one primary measure plus quality guardrails; compare like-for-like cohorts and disclose missing data. Treat estimates as scenarios, not observed outcomes.

Risks and controls

Check relevance, consent, disclosure, workload and downside before scaling. Keep an evidence trail, obtain human review for material commitments, and pause if trust, quality or compliance signals deteriorate.

Next steps

1. Confirm the goal, audience and available capacity.
2. Gather the minimum evidence for a first test.
3. Assign an owner, budget and review date.
4. Run a small pilot, record outcomes and decide whether to iterate, expand or stop.