[type] 在打字稿/流程中是什么意思？

Question

I've recently stumbled upon an old code of mine, I noticed I had incorrect typing there.

interface OptionType {
   label: string,
   value: OptionValueType
}

interface Props {
  options: [OptionType] // < this is wrong
}

Now obviously, this should have been OptionType[] or Array<OptionType> , but curiously enough, the code here, at least according to both linter ( eslint ) and compiler is valid syntax.

So, what exactly does [OptionType] represent?

My best guess would be an index/element of an array, akin to destructuring, but that feels odd as there's no original array reference in the syntax

Answer 1

It's a tuple. It's syntax allows you to specify an array with exactly n elements, and give a type for each:

const myTuple: [string, number] = ['foo', 5];