Beginner's TypeScript Section 18 exercises

Two Ways to Represent Arrays

There are two solutions to this problem.

Add Square Brackets

The first solution is to add a couple of square brackets to Post:

// inside the User interface
posts: Post[];

Now if we create a posts consts of the type Post[], we'll get autocomplete when we populate the `i

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0:00 There are two solutions to this problem. The first one is to add a couple of square brackets just at the end of Post here. That turns it into an array of posts. I can extract this into a type itself. I can say const posts is Post array. Now, we get to specify all the array of posts, and I get my stuff all autocompleted for me, which is really, really nice. That's the first type of syntax you can use.

0:28 There's a second type of syntax which specifies that using...This is what's called a generic type. This array type here is something I don't have to import from anywhere. It's just inside the language. If I misspell it, then I'm going to get an error there, obviously, but array just is available globally.

0:48 What I do here is I pass it the thing that I want to put in the array. It's an array of posts. This little square...Not square brackets. I can't remember the name for them, but these little braces here, whatever they're called, this syntax is very, very common in especially more advanced types. I want to point this out.

1:11 It's up to you which one you use. They resolve into exactly the same thing. It's just two different ways of expressing the same thing. I like this one, but then I wanted to teach this one because it comes up a lot later, especially with promises, especially with maps, sets, records, things like that. Do get used to this syntax. That's the main way to express arrays in TypeScript.