How to specify the type of an array consisting of number and an array in typescript?

Question

I have the following data structure which I want to pass as a parameter into a function.

let structure = [6, [197,47,28,191,198,129,117,82,171]]

It's given that the first element is always a number and the second element an array of numbers. When I want to pass it to my function, my IDE suggests following as input types:

function myFunc(structure:(number | number[])[]) {
    ....
}

This leads to problems because it is not specific enough. I know the first element is always a number, but based on my type declaration it doesn't have to be.

How do you declare the type here properly in typescript?

Answer 1

function myFunc(structure: [number, number[]]) {
    ....
}

This is called a tuple type.