TypeScript

Type Check Commands

Run TypeScript type checks to catch errors before runtime. Learn to check entire projects, individual files, and integrate type checking into your CI pipeline.

12 commands

Pro Tips

Use 'tsc --noEmit --pretty' for colorized error output that's easier to read in the terminal.

Add 'tsc --noEmit' to your CI pipeline and pre-commit hooks to catch type errors before merge.

Use '// @ts-check' at the top of .js files to get TypeScript checking without converting the file.

Common Mistakes

Don't use '// @ts-ignore' to suppress errors without understanding them. Use '// @ts-expect-error' with a comment instead.

Type checking a large project can be slow. Use project references to check subsets independently.

Commands

Type check only

$ tsc --noEmit

Validate types without generating JavaScript files.

Type check in watch mode

$ tsc --noEmit --watch

Continuous type checking in background.

Enable strict mode

$ tsc --noEmit --strict

Type check with all strict options enabled.

Check null/undefined

$ tsc --noEmit --strictNullChecks

Treat null and undefined as distinct types.

Check implicit any

$ tsc --noEmit --noImplicitAny

Error on expressions with implied 'any' type.

Check unused locals

$ tsc --noEmit --noUnusedLocals --noUnusedParameters

Error on unused variables and parameters.

Incremental type checking

$ tsc --noEmit --incremental

Fast type-check only with incremental compilation cache.

Clean watch output

$ tsc --preserveWatchOutput

Preserve console output in watch mode instead of clearing screen.

Custom build info file

$ tsc --tsBuildInfoFile .tsbuildinfo

Specify custom location for incremental compilation cache file.

Skip library checks

$ tsc --skipLibCheck

Skip type checking of all declaration files (*.d.ts) for faster builds.

Optimize rebuild speed

$ tsc --assumeChangesOnlyAffectDirectDependencies

Assume file changes only affect direct imports (faster, less safe).

Incremental with cache

$ tsc --incremental --tsBuildInfoFile .cache/tsbuildinfo

Full incremental compilation with custom cache directory.