Creating union types

In this lesson, we'll learn what a union type is, how to create one and some cases where they are useful.

Understanding a union type #

As the name suggests, union types are types that we can combine together to form a new type. A union type is constructed from existing types using the pipe (|) character:

type A_or_B_or_C = A | B | C;

Let’s go through an example to make this clear. Let’s say we have an age variable that can be null or numeric. How could we create a type for this? Well we can combine the number and null types in a union type as shown below:

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