TypeScript Best Practices for 2024
Embrace Strict Mode
Always enable strict mode in your tsconfig.json. This includes strictNullChecks, strictFunctionTypes, and other strict flags. While it may seem restrictive at first, strict mode catches entire categories of bugs at compile time. It forces you to handle null and undefined explicitly, prevents implicit any types, and ensures your code is more predictable. The initial investment in stricter types pays dividends in reduced runtime errors.
Leverage Type Inference
TypeScript's type inference is powerful—use it. Don't annotate types when TypeScript can infer them correctly. Over-annotation makes code verbose and harder to maintain. Let TypeScript infer return types for functions, variable types from initializers, and generic parameters when possible. Explicit types are valuable for function parameters, public APIs, and when inference produces types that are too wide or too narrow.
Use Discriminated Unions
Discriminated unions are one of TypeScript's most powerful features for modeling complex state. Instead of using optional properties or multiple boolean flags, create union types with a discriminant property. This enables exhaustive checking and makes impossible states unrepresentable. Your code becomes more type-safe and easier to reason about because TypeScript can narrow types based on the discriminant.
Avoid Type Assertions
Type assertions (as Type) should be a last resort. They tell TypeScript 'trust me, I know better,' which defeats the purpose of type checking. Instead, use type guards, discriminated unions, or refactor your code to make types flow naturally. If you find yourself using many assertions, it's often a sign that your type definitions need improvement. When assertions are necessary, document why with a comment.
Great TypeScript code is about working with the type system, not against it. By following these practices, you'll write code that's not only type-safe but also more maintainable and easier to refactor. The time invested in good types is time saved debugging production issues.
David Park
Software developer and writer sharing insights on modern web development.