typescript

Enable incremental compilation, skipLibCheck, and project references in tsconfig.json for 50-90% faster rebuilds. Also configure include/exclude properly to prevent scanning unnecessary files, and use isolatedModules for faster single-file transpilation with bundlers.

Avoid deeply nested generic types and large union types, which cause exponential instantiation and quadratic comparison costs. Extract conditional types to named aliases to enable compiler caching, and prefer interfaces over type intersections for 2-5× faster resolution.

Prefer interfaces over type intersections because they resolve 2-5× faster during type checking. Interfaces create named types the compiler caches, while intersections force repeated structural comparison of all members.

Await inside loops creates N sequential operations, so 10 iterations at 100ms each take 1000ms total. Use Promise.all with map() to run independent operations in parallel, reducing wall-clock time to the slowest single operation.

No, it explicitly excludes TypeScript basics, framework-specific patterns, and testing. It focuses on performance optimization, compiler configuration, type safety, async patterns, and memory management for existing TypeScript code.

Use unknown whenever the type is not known at compile time, such as JSON parsing or API responses. Unlike any, unknown forces explicit type narrowing through type guards before operations, preventing runtime errors from unsafe property access.