TypeScript best practices. Use when reading or editing any .ts or .tsx file.
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What the file says
# TypeScript best practices
Apply the **type-system-discipline** principle skill first.
| Rule | Summary |
|------|---------|
| Discriminated unions | Model variants with a `kind` literal discriminant so impossible states can't be represented. No optional-field bags. |
| Branded types | Brand primitives with `& { readonly __brand: "X" }` so they can't be mixed up. Validate once at the boundary. |
| Constructive modeling | Build the shape so the illegal value can't be constructed. `[T, ...T[]]` for non-empty, `[T, T][]` for even length, `start` plus `duration` for a range. Not a runtime guard, not a wish for refinement types. |
| Simplest total type | Keep `T[]` while every operation on it stays total. Strengthen to `NonEmpty<T>` only where the loose type forces `!`, a cast, or a "should never happen" throw. |
| `unknown` over `any` | External data is `unknown`. |
| Schemas before guards | Before hand-writing a property-by-property type guard, use the repository's runtime schema library and infer the type from the schema, such as `z.infer`. |
| No `as` casts | Every `as` is a runtime crash waiting. Cast only after validation. |
…
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Source
GitHub
creedants/pstack-t3 · 15 stars · license MIT · pushed 2026-10-19 · branch main
API
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