Why Strict TypeScript Is Kindness to Future You
The type system whispers before production shouts. `strict: true` is a friend who won't let you send the email unproofread.
[ essay ]
TypeScript does not raise its voice. It underlines in red and waits. That patience is the most underrated mentorship in modern tooling — and the first line of defense when generated code arrives fluent and wrong.
Thesis
Strict types are documentation that runs before merge. Kindness to future you is refusing to ship uncertainty you could have caught at compile time.
This essay pairs with Types Are Documentation That Runs — that piece is the micro argument in one breath. This one is how to adopt strictness without a rewrite fantasy.
Context
Mixed JavaScript and TypeScript repos often keep strict: false as a temporary measure that becomes permanent policy. The cost shows up later: null dereferences in payment paths, props that drift between React components, API clients that accept anything because any was faster in March.
Adding LLM-generated scaffolds raises the stakes. Models name fields convincingly and miss discriminated unions entirely. A strict compiler is the reviewer that never tires — if you leave it enabled.
Mechanism
Treat the squiggle as design feedback
The underline means “your mental model and the code disagree.” Fixing it is cheaper than explaining the outage. Teams that batch-suppress errors train everyone to ignore whispers until production shouts.
Enable strict as a bundle, then fix module by module
strict: true turns on the flags that matter together: null checks, implicit any rejection, function type strictness. You do not need a big-bang rewrite — you need a bounded surface per PR with CI enforcing no new escapes.
interface Transmission {
signal: string;
frequency: number;
encrypted: boolean;
}
Interfaces outlive the feature that introduced them. Let the type system hold that memory.
Replace any with intentional boundaries
Prefer unknown and narrow at IO edges. Use generics for reusable utilities. When JavaScript interop forces an escape hatch, comment the debt and ticket the removal — silent any exports confusion to every importer.
Use types as the first AI review pass
Before human review, run tsc. Wrong keys, impossible states, and missing null handling become compile errors instead of demo magic. Pair strict TypeScript with tests — types prove shape; tests prove behavior.
Tradeoffs
Short-term velocity vs long-term calm. Loose configs win the sprint until the first null crash in prod.
Codegen vs hand-written types. OpenAPI and GraphQL schemas as source of truth reduce drift; hand-maintained DTOs rot quietly.
Gradual strictness. checkJs on legacy files plus // @ts-expect-error with owner tags beats pretending migration finished because the folder renamed.
Close
Deep currents move oceans without announcement. Strict types hold shape while features churn above — if you stop disabling the current.
Enable one strict flag you have been deferring. Fix one module. Ship the PR before the exception becomes culture.
— JV · Dark Heart Labs.