RuntimeTypeChecks | Runtime type checks for JavaScript and TypeScript

RuntimeTypeChecks is a TypeScript library. RuntimeTypeChecks has no bugs, it has no vulnerabilities, it has a Permissive License and it has low support. You can download it from GitHub.

A reasonably-typed TypeScript application gives the developer enough confidence that the operations within the applicaiton are safe and predictable. As a result, you rarely see the undefined is not a function errors, which is often caused by passing a wrong type of object. This is because the TypeScript type checker ensures that you only invoke functions with compatible parameters. The type checker, however, cannot verify this at the application or module boundary, where the application receives data from the backend, a web-worker, or just another module. Here, we cannot know statically if the data is correct. So we just have to trust that it is. For example, imagine an application invoking some Session module to get the end date of the last session. If our understanding of the Session library is incorrect and lastSessionEnd is a string, not a date, then we may get an exception somewhere deep inside the invokeBusinessLogic function. Or what is even more likely, the type of an object changes with a new version of the Session library. This is possible because the Session library is not maintained by us. To check that the session data entering our well-typed application is correct, we can use the Runtime Type Checks library. It allows us to decorate our application boundary to make sure that the objects are of the right type or the right shape. This will check at runtime that lastSessionEnd is a date. If not, calling getLastSessionEnd will throw an exception.