How to implement class constants?

How to Implement Class Constants in TypeScript 🚀

Have you ever found yourself in a situation where you wanted to declare a constant property in your TypeScript class? 🤔 You tried using the const keyword, only to be met with the dreaded "A class member cannot have the 'const' keyword" error. 😱 Don't worry, you're not alone! Many TypeScript developers have faced this issue and wondered if there's a better way to achieve class constants. 🤔

In this blog post, I'll show you an easy and elegant solution to declare class constants in TypeScript, even if you're using an older version. 💪 Let's dive right in! 🏊‍♂️

The Problem and Your Workaround 🌩️

Initially, the TypeScript const keyword cannot be used to declare class properties. This limitation can be frustrating, especially if you want to clearly indicate in your code that a property should not be changed. 😤

While you've been using a read-only property as a workaround, you've been wondering if there is a better way. For example, you've been using the following code to declare a constant property:

get MY_CONSTANT(): number { return 10 };

While this workaround gets the job done, it may not be the cleanest or most intuitive solution. Luckily, I have some fantastic news for you! 🎉

The Solution: readonly Modifier 🌟

Starting from TypeScript 2.0.3, the readonly modifier was introduced to support class-level constants. This change enables you to declare a property and ensure it cannot be changed after it has been initialized. 🙌

Here's how you can implement class constants using the readonly modifier:

class MyClass {
    readonly MY_CONSTANT: number = 10;
}

By prefixing the property with the readonly keyword, you explicitly convey that the value of the property should remain constant throughout the class's lifetime. 🚫

Fallback for Older TypeScript Versions 👴

In case you're working with an older version of TypeScript that doesn't support the readonly modifier, don't worry! There's still a way for you to declare class constants. 😎

You can use the Object.freeze() method to prevent modifications to an object, effectively achieving immutability. In this case, the object will hold your constant properties. Here's an example:

class MyClass {
    static readonly MY_CONSTANT = Object.freeze({
        MY_PROP: 'value',
        MY_OTHER_PROP: 10,
    });
}

By using Object.freeze(), you can ensure that the properties of the object remain constant, providing a similar effect to class constants.

Call-to-action: Share Your Experience! 🗣️

Now that you know how to implement class constants, it's time for you to put it into practice and share your experience! 😄 Have you encountered any other tricks or tips to declare class constants in TypeScript? Let us know in the comments section below! ⬇️

If you found this blog post helpful, don't keep it to yourself! Share it with your fellow TypeScript developers who might be struggling with the same issue. Let's spread the knowledge! 🤝💡

Until next time, happy coding! 💻✨