TypeScript Strict Mode Survival Guide

Strict mode in TypeScript is the difference between "TypeScript is just JavaScript with types" and "TypeScript actually catches bugs before they hit production." When you set "strict": true in tsconfig.json, you enable a bundle of compiler flags that dramatically improve type safety. But migrating an existing codebase to strict mode can feel overwhelming. Hundreds or thousands of new errors appear overnight. This guide walks you through every strict flag, explains what each one catches, gives you patterns to fix the most common errors, and provides a phased migration strategy that will not block your team for weeks. The strict flag enables these individual options: strictNullChecks, strictFunctionTypes, strictBindCallApply, strictPropertyInitialization, noImplicitAny, noImplicitThis, alwaysStrict, and useUnknownInCatchVariables.