Why you should make sure that your function params are extensible

For critical functions which you feel will change a lot in the future best to avoid primitive types directly in params and use extensible objects.

Making response objects extensible#

Rather than returning primitive types directly, wrap responses in objects:

// Option 1 - not extensible
class DbUser {
    name: string;
    age: number;
}
function getUser(id: string): DbUser

// Option 2 - extensible
class APIUserResponse {
    user: DbUser
}
function getUser(id: string): APIUserResponse

The second option sounds better as you can simply add error state / tasks in the UserResponse object without requiring frontend and backend refactoring.

Making requests extensible#

Rather than accumulating function parameters, use objects for request handling:

// Hard to read, hard to extend
getUser('1', false, none, true);

// Self-documenting, easy to extend
getUser({
    id: '1',
    includeDisabled: false,
    includeTasks: true
})

The second approach is significantly more readable and maintainable.

Key takeaway#

For critical functions which you feel will change a lot in the future best to avoid primitive types directly in params and use extensible objects. Primitive types lack extensibility, while context-dependent objects can provide it.