Array Typing

TypeScript is known for its type system. That's why it's called TypeScript.
© The Author of this course

In previous chapters, we've already seen how to type arrays.

But first, let's answer one question: why do we even need typing for arrays?

Let's take an example of a bookshelf. We buy a bookshelf and start putting various books on it. But as time goes by, we start putting other random items there as well, like medals, cups, boxes, and so on. Eventually, our bookshelf stops being just a bookshelf and becomes a regular shelf.

This is where typing comes in. If we decide that our bookshelf should only contain books, we specify that as the type.

For example:

javascript
Copia codice
Collapse
let bookshelf: book[] = [`book names`]

So, we've defined that the bookshelf will exclusively contain books.

Note

There is no such type as book[]; I made it up to make the example more understandable.

If you've bought a bookshelf not just for books but also for figurines, for example, then you can type the bookshelf array with multiple data types, like this:

javascript
Copia codice
Collapse
let bookshelf: (book | figurines)[] = [data];

So, we've defined that the bookshelf will store not only books but also figurines.

We can do the same with a real-world case when creating an array. For example, we need to store numerical values and strings, like this:

We used 2 different types when declaring the array. We mixed numbers and fruits.
Why?
I don't know.