Demystifying TypeScript Discriminated Unions

Demystifying TypeScript Discriminated Unions

Discriminated unions in TypeScript are a powerful feature that can help make your code more organized and easier to read. They allow you to break up complex union types into multiple parts, each of which is associated with a unique type. This makes it much easier to understand and use complex data structures in your code.

Discriminated unions are best described as a way of creating an object that contains different types of information. For example, if you have a list of values (such as numbers or strings) that represent different types of data, you can create a discriminated union to store each one of these types in its own property. This will make the structure of the data more organized and easier to process.

To define a discriminated union, you need to first provide a type literal for each of the properties in the union. Then, you must specify a discriminant property that uniquely identifies each type. Finally, you need to specify the types of each of the properties. The resulting union will look something like this:

type MyUnion = { 
  discriminant: 'A' | 'B' | 'C', 
  numberValue: number, 
  stringValue: string
}

Now, when you want to use an instance of this union, you can easily identify which type of data it contains using the discriminant property. For instance, if the discriminant is 'A', you know that the union contains a number value. Similarly, if the discriminant is 'B', you know that the union contains a string value.

Discriminated unions are incredibly useful when it comes to working with data in TypeScript. They allow you to create complex data structures without having to write extra code. Plus, they make it easy to keep track of what type of data is in a given union, making it easier to debug and maintain your code.