Programming TypeScript

Appendix F. TSC Compiler Flags for Safety

Tip

For a complete list of available compiler flags, head over to the TypeScript Handbook website.

Each TypeScript release introduces new checks that you can enable to squeeze even more safety out of your code. Some of these flags—prefixed with strict—are included as part of the strict flag; or, you can opt into strict flags one at a time. Table F-1 lists the compiler flags related to safety that are available at the time of writing.

Table F-1. TSC safety flags

Flag	Description
alwaysStrict	Emit 'use strict'.
noEmitOnError	Don’t emit JavaScript when your code has type errors.
noFallthroughCasesInSwitch	Make sure that every switch case either returns a value or breaks.
noImplicitAny	Error when a variable’s type is inferred as any.
noImplicitReturns	Make sure that every code path in every function explicitly returns. See “Totality”.
noImplicitThis	Error when you use this in a function without explicitly annotating the this type. See “Typing this”.
noUnusedLocals	Warn about unused local variables.
noUnusedParameters	Warn about unused function parameters. Prefix your parameter name with _ to ignore this error.
strictBindCallApply	Enforce type safety for bind, call, and apply. See “call, apply, and bind”.
strictFunctionTypes	Enforce that functions are contravariant in their parameter and this types. See “Function variance”.
strictNullChecks	Promote null to a type. See “null, undefined, void, and never”.
strictPropertyInitialization ...