The problem of Enums in TypeScript

Table of contents

Enums: A Deceptive Pitfall

Enums, short for enumerations, appear intuitive at first glance. They are present in various programming languages and are designed to represent a set of valid values. For instance, an enum defining user roles (e.g., user, subscriber, admin, and staff) seems like a natural choice. However, the devil is in the details.

When utilizing enums, the default value for the first element is often set to zero. This seemingly harmless default becomes problematic when developers try to use logical checks, leading to unexpected and, frankly, cursed behavior.

enum UserRole {
  User, // 0 by default
  Subscriber,
  Admin,
  Staff,
}

const userRole = UserRole.User;

// The following condition will never be true due to falsy nature of UserRole.User
if (userRole === UserRole.User) {
  console.log("This will never get executed!");
}

A Better Alternative: Leveraging TypeScript’s Strengths

TypeScript provides a more elegant and reliable solution without sacrificing the benefits of enums. Instead of relying on enums, let’s leverage TypeScript’s type system to create a more explicit and type-safe representation of the valid values.

// Using TypeScript's type system to define the user roles explicitly
type UserRole = "user" | "subscriber" | "admin" | "staff";

const userRole: UserRole = "user";

// Now, logical checks work as expected without unexpected falsy behavior
if (userRole === "user") {
  console.log("This will be executed as expected!");
}

By using a combination of constant arrays and type definitions, developers can achieve the same goals as enums while avoiding the associated problem. This approach ensures a more straightforward developer experience and eliminates the need to wrestle with quirky enum behaviors.

Iteration and Strict Typing: A Winning Combination

Let’s tale a look at a practical example of handling user roles without enums. By using an array of constant values and defining a type based on those values, developers gain the ability to iterate through roles easily. The resulting code is more readable, maintainable, and less prone to unexpected behavior.

// Creating an array of constant values for user roles
const userRoles = ["user", "subscriber", "admin", "staff"] as const;

// Defining a type based on the array to ensure strict typing
type UserRole = (typeof userRoles)[number];

// Iterating through user roles becomes straightforward
userRoles.forEach(role => {
  console.log(`Processing role: ${role}`);
});

Conclusion

By embracing alternative approaches that leverage TypeScript’s strengths, developers can create more robust and predictable code. As the programming community continues to evolve, it’s essential to reevaluate established practices and adopt more efficient solutions when they arise. So, the next time you consider using enums in TypeScript, think twice and explore alternative patterns for a smoother development experience.