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Learn how to check values against a group of enum values in TypeScript, using effective and modern techniques without the need for excess helper classes.
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How to Check Values Against Enum Sets in TypeScript

Using enumerations (enums) can streamline code by giving meaningful names to numeric values, but when it comes to checking if a specific value belongs to a particular group of enums, things can get a bit tricky. In this post, we'll explore how to efficiently check if a value exists within a set of enums in TypeScript.

The Problem

In many programming languages like Java, enums can easily be grouped together. For instance, you can define an Animal enum with values like CAT, DOG, etc. If you want to check whether an animal is a mammal, Java allows you to do this using EnumSet. The critical question arises: How can we achieve the same functionality in TypeScript? Without creating a helper class for each enum, which can become cumbersome, especially with multiple enum types?

Here’s an example of a Java usage:

[[See Video to Reveal this Text or Code Snippet]]

Alternative Approaches in TypeScript

Your initial attempt might look like this:

[[See Video to Reveal this Text or Code Snippet]]

While combining the enum with the group in a namespace does unify the structure, it requires defining both separately, and namespaces in TypeScript are considered somewhat outdated.

The Best Solution: Using Set

Enums in TypeScript serve as syntactic sugar for string or number literals, making it easy to use other common JavaScript types. A Set is a perfect fit for our needs. Here's how you can implement it:

Step-by-Step Implementation

Define the Enum:
Create your enum just as you would normally.

[[See Video to Reveal this Text or Code Snippet]]

Group Enums Using a Set:
Utilize the Set data structure to hold the enum values.

[[See Video to Reveal this Text or Code Snippet]]

Checking the Value:
You can easily check for membership using the has method from the Set.

[[See Video to Reveal this Text or Code Snippet]]

Optional Namespace Merging:
If you still want to access the mammals through the enum, you can use namespace merging:

[[See Video to Reveal this Text or Code Snippet]]

Now, you can check memberships like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

As you can see, using a combination of TypeScript enums and the Set data structure allows for a clean and efficient way to check values against a group of enums without the overhead of unnecessary classes or outdated structures. This approach keeps your code simple, readable, and maintains the benefits of using enums.

Feel free to implement these strategies in your TypeScript projects to handle enum checks effectively!