Picture this scenario: You have a class A with a method that can create an instance of class B. You're unable to make any changes to the code of either A or B, as they are part of an external library.
In this situation, if you want to enhance the functionality of B, one approach could be to create a new class C that extends B and implement the new features there. However, even if you do this, the method in A that returns an instance of B will still return B and not the modified version in class C. To address this issue, you might need to create another class D that extends A and overrides the method returning B to now return C. But this can become overwhelming especially if classes E-Z also have methods returning an instance of B which you would like to include in C as well.
Unlike other languages, Rust offers extension traits to expand the functionalities of a struct by adding new methods, making them accessible to all instances of that struct. In our previous example, we could define a new trait called BExt for B and the instance returned by A's method would now have the methods implemented in BExt. Is it feasible to achieve something similar in TypeScript? Can you add a method to all instances of a class without altering its original implementation? Alternatively, is there a way to extend a class's functionality so that all methods returning an instance of the class come with the extended capabilities?
For instance:
//lib.ts
class B {}
class A {
static getB(): B { return new B(); }
//index.ts
import {A, B} from "lib.ts"
//Add a new method to B somehow:
addMethod(B, "helloWorld", () => console.log("Hello World"));
A.getB().helloWorld() // okay;
Keep in mind that the addMethod function shown here is just an illustrative example and doesn't necessarily have to be an actual function; it simply demonstrates a way to append a new method to B.