I want to create a parameter decorator that can transform the parameter value passed by the user from a string to a number:

class foo{     
  something(@ToNumber id: string){
    console.log(id)   
  } 
}

So I made this function (decoarator):

const ToNumber =
  (target: any, propertyKey: string, parameterIndex: number) => {
    const originalMethod = target[propertyKey];
    target[propertyKey] = function(...args: any[]) {
        args[parameterIndex] = parseInt(args[parameterIndex]);
        return originalMethod.apply(this, args);
    }
}

Anyway it did not work, and the output when running the something method is still a string:

const instance = new foo()
instance.something("123")

In the terminal:

[LOG]: "123"  # as a string

Here is a typescript playground

I don’t know if this extra info helps, but I read something in the past about the Reflect class, but I wasn’t able to know how to integrate it into my decorator or if it’s useful in this case or not.