Types vs Interfaces in TypeScript: Making the Right Choice

Introduction

The TypeScript community has long debated the use of types and interfaces. Developers often wrestle with the decision of when to use one over the other. In this blog post, we'll explore the advantages and drawbacks of both, helping you make an informed choice that aligns with your coding style and project needs.

Phase One: Interfaces Are the Bomb

In the early days, interfaces were the favored option. The TypeScript Performance Wiki even claimed that interfaces were faster than types. It was believed that interfaces could boost the speed of the TypeScript type checker, making them ideal for performance-critical projects. However, interfaces had their limitations, primarily being designed for objects and functions.

Performance Considerations

It's important to clarify that when we talk about "speed," we're referring to the efficiency of the TypeScript type checker, not the runtime performance of your code. For large projects, a slow type checker can be a significant issue, pushing developers towards interfaces for potential performance improvements.

Benchmarking

To test this belief, a benchmark was conducted, comparing a thousand types to a thousand interfaces. The results were inconclusive and led to discussions with the TypeScript team, revealing new insights.

// Using an interface
interface Point {
  x: number;
  y: number;
}

// Using a type
type Coordinates = {
  x: number;
  y: number;
};

Phase Two: Consistency Is Key

Phase Two introduced a different perspective: the choice between types and interfaces doesn't matter as long as you maintain coding consistency. This viewpoint encouraged using interfaces for objects and types for other constructs, sparking debates in the TypeScript community.

Interface Inheritance

One key advantage of interfaces is their ability to inherit from other interfaces, a feature not easily achieved with types.

interface Shape {
  color: string;
}

interface Circle extends Shape {
  radius: number;
}

Phase Three: The Need for Specific Features

A turning point occurred when the inventor of AngularJS encountered issues with interfaces, especially regarding appending properties, which led to unpredictable behavior.

Declaration Merging

Interfaces introduced "declaration merging," a valuable feature in some scenarios but one that could add complexity when different interfaces shared the same name and scope.

interface Product {
  name: string;
  price: number;
}

interface Product {
  description: string;
}

Conclusion: Making the Right Choice

In Phase Three, the ultimate recommendation is to use types unless you specifically need features provided by interfaces. Types offer predictability and are less likely to exhibit unexpected behavior. Importantly, there is no discernible performance difference between types and interfaces.

Consider Your Needs

Your choice between types and interfaces should align with your project's unique requirements and your personal coding style. If you need inheritance, want to extend another type, or come from an object-oriented programming background, interfaces may be your preferred choice. However, if predictability and control are your priorities, types are the more suitable option.

In summary, there is no one-size-fits-all solution. Your choice should be guided by your project's demands and your familiarity with TypeScript's intricacies.

So, the next time you face the decision of types vs. interfaces in TypeScript, remember this post. Let it guide you in making an informed choice that best fits your coding style.

Happy coding! Like, subscribe, and stay tuned for more enlightening content.