I’m working on some type guards for an API framework and want to connect the path parameters (a string) to a validation object.

I have the following code (nb. this is a simplified version, there are more types allowed than just number or bigint, like time periods, etc.) :

Consider the following code:

I’m just playing around with TypeScript and wrote this:

A JavaScript Map object has the type Map<K, V>. I would like to create a type that matches V.

Here my generic function defc

Consider the following Typescript function:

I store data in objects with different versions that use different keys and different types. The acceptable types for the data properties are defined in an interface that defines the versions as a dictionary type. I want to match the object with handler functions based on a matching key in the data. I create a dictionary value of handlers that stores the functions indexed by the associated key. I have a generic handle function that takes one of the data objects, a dictionary of all handlers, and a callback that receives a matching value and handler function.

I have a function createUnion that takes an array of callbacks with different return types and returns one of the results. I want it to return a union of the return types. It works perfectly when combining types with null or undefined, but not other types. They are not even done in order precedence. How can I correctly infer the union type from all the callbacks?

I have an interface that takes a generic type input called Data