I’m working with TypeScript and trying to ensure that the return type of a function accurately reflects the properties that are present in the input object after mapping. Specifically, I want TypeScript to enforce type constraints so that accessing non-existent properties on the returned object results in a compile-time error.

I am trying to use a template literal type for the return type of a generic function which doesn’t seem to work well when indexing on the type parameter.

So I have a dictionary with functions and the arguments of those functions, like this:

I have react-router v6 in my app, and i want all paths in router config object to be absolute

I would like to have a function whose input object keys are statically typed depending on the given value of some key. Here is a TypeScript playground with a failing test:

I have a type that I’m trying to make dynamic. I currently have a hardcoded version that looks like this:

I have a function where TypeScript can infer the return type based on the type of the input parameters.

I’m working to create a Prisma extension. For reasons, I started with JavaScript, using JSDoc hints for typing. The extension actually works just fine; however, the type hints are terrible, which led me to believe I was doing something wrong. In fact, when I switched to a typescript transpiler, all sorts of errors appeared in my declaration files that were invisible when using esbuild. My biggest current challenge in squashing these is, I need to use a value provided by the user when the initial extension is instantiated as a key in various other type declarations in my declaration files.

I am a beginner in Typescript. I am trying to learn generics.

Say I want to extend the Promise class with an overriden then() method that does something before calling super.then():