Track

TypeScript

Review type narrowing, API boundaries, unions, and safer function shapes.

01
Type inference and explicit boundaries
Let TypeScript infer local values, but type the boundaries other code depends on.
inferenceboundariesapi-design
02
Narrowing unknown
Check unknown values before using them as trusted application data.
unknownnarrowingruntime-data
03
Avoiding unsafe assertions
Prefer checks that prove a value's shape over assertions that silence the compiler.
assertionssafetyruntime-data
04
Discriminated unions
Model related states with a discriminant so callers can narrow safely.
unionsstatenarrowing
05
Exhaustive checks with never
Make every union case handled so new states fail loudly during development.
unionsexhaustivenever
06
Precise function types
Describe callbacks with the arguments and return value the caller actually supports.
functionscallbacksapi-design
07
Optional properties vs nullable values
Use optional and nullable fields to describe different kinds of absence.
optionalnullabledata-modeling
08
Generic constraints
Constrain generics to the fields the function actually needs.
genericsconstraintsapi-design
09
Utility types at API boundaries
Derive focused request and view types from domain types without exposing everything.
utility-typesapi-designboundaries
10
Type-only imports and module boundaries
Separate type dependencies from runtime dependencies so modules stay lightweight.
importsmodulesboundaries