How can I use unions with type aliases in TypeScript?

How can I use unions with type aliases in TypeScript?

You can create a type alias that uses a union to define a type that can be one of several types. For example, type ID = string | number; allows ID to be either a string or a number.

Can you give me an example of how to use that in a function?

Sure! Here's a simple function:

function printID(id: ID) {
    console.log(`The ID is: ${id}`);
}

This function accepts an ID which can be either a string or a number.

What if I want to add more types to the union?

You can easily extend the union. For example, type ID = string | number | null; now allows ID to also be null.

Is there a way to check the type of the union in the function?

Yes! You can use the typeof operator to check the type. For example:

if (typeof id === 'string') {
    // handle string case
} else if (typeof id === 'number') {
    // handle number case
}