Establish a default value for a TypeScript generic Type: distinguishing between 'unknown' and 'any'

Question

An interface has been created with a parameter that takes a generic type input named Data

export interface MyStructure<Data> {
  id: string;
  data: Data;
}

The goal is to allow the Data type to be optional in order to support scenarios like:

function printId(obj: MyStructure): void {
    console.log(obj.id);
}

In certain contexts like printId, specifying the generic type for MyStructure<Data> is not necessary.

The question arises on how to handle this situation: should the default be set to any or unknown, and what are the implications.

export interface MyStructure<Data = unknown> {
  id: string;
  data: Data;
}

export interface MyStructure<Data = any> {
  id: string;
  data: Data;
}

Answer 1

Answer №1

When deciding between using Data = unknown and Data = any, it's important to consider the following distinctions:

unknown: Offers enhanced type safety by limiting the operations that can be performed on the data property unless its type is explicitly checked first, reducing the risk of misuse
any: Permits virtually any type of operation on the data property, potentially leading to unexpected runtime errors.

Overall, opting for unknown would be the preferable choice.

export interface MyStructure<Data = unknown> {
  id: string;
  data: Data;
}

Answer 2

When deciding between using Data = unknown and Data = any, it's important to consider the following distinctions:

unknown: Offers enhanced type safety by limiting the operations that can be performed on the data property unless its type is explicitly checked first, reducing the risk of misuse
any: Permits virtually any type of operation on the data property, potentially leading to unexpected runtime errors.

Overall, opting for unknown would be the preferable choice.

export interface MyStructure<Data = unknown> {
  id: string;
  data: Data;
}