The non-null assertion operator (!) tells TypeScript to trust you when you say a value isn't null or undefined. But this trust comes at a cost: runtime crashes that TypeScript could have prevented. Learn why this operator undermines type safety and what to use instead.
Running into the TypeScript error "Type undefined is not assignable to type string"? It's a frequent error when variables might be undefined but functions demand strings. Fix it with string concatenation, templates, or assertion functions.
This article explains how to filter arrays in TypeScript while maintaining correct types. It demonstrates how to create a type guard to ensure that the filtered array only contains the desired type. It also discusses the downsides of type guards and compares them to assertion functions.
An assertion function is a runtime check that identifies the type of unknown input. TypeScript's compiler assumes the input is of the type claimed by the assertion function's signature. Assertion functions are useful for uncertain values, like user input, and generate runtime checks. They can raise errors if the input doesn't meet criteria.
TypeScript 3.4 introduced const assertions, which allow you to claim a value as immutable. This is useful when working with arrays, as it prevents new values from being added to an existing array.