TypeScript Tricks

Objects and Classes

TS Enums

Using TypeScript Enums

TypeScript enums define named constants with numeric and string variants.

Introduction to TypeScript Enums

Enums in TypeScript are a way to define a set of named constants. They can be used to create a collection of related values, both numeric and string types, which can enhance code readability and intent.

Enums are particularly useful when you have a set of values that are closely related and you want to use descriptive names for these values rather than numbers or strings directly.

Numeric Enums

Numeric enums are the default in TypeScript. They start with a value of 0 and increment by 1 for each member. You can also specify values manually.

Here's an example of a numeric enum:

In the above example, Direction.Up has the numeric value 0, Direction.Down is 1, and so on. You can also start the enum at a different number, like this:

In this case, the enum values will start from 1, and the rest will increment sequentially.

String Enums

String enums are more explicit than numeric enums and are useful when you want to represent a set of values with meaningful string names.

Here's an example of a string enum:

In this example, each enum member is initialized with a string literal, which means you can use these names directly in your code, making it more readable.

Heterogeneous Enums

TypeScript also supports enums that mix numeric and string values, known as heterogeneous enums. This is generally discouraged as it can be confusing, but it might be useful in specific scenarios.

Here's an example:

In this enum, No is a numeric value, while Yes is a string.

Using Enums in TypeScript

Enums can be used in various ways in TypeScript. They can serve as function parameters, switch case conditions, or any scenario where a fixed set of options is needed.

Here's an example of using an enum in a function:

By using enums, you make your code more descriptive and reduce the risk of using invalid values.

Conclusion

TypeScript enums are a powerful feature that allows developers to define a set of named constants, whether numeric or string-based. They improve code readability and intent, making it easier to maintain and understand.

While numeric enums are the default and can be convenient, string enums often provide more clarity. Use heterogeneous enums cautiously and only when necessary to avoid confusion.

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