TypeScript tuple with array element

Question

TypeScript newbie here. I did some quick searching but was unable to find an answer. The question is this: what is the proper definition for an array of tuples, where the first tuple element is a string, and the next is an array of numbers? I've tried this:

type labeledValuesType = [string, number[]]

 constructor(headings: string[], rows: Array<labeledValuesType>) {...

But in VS Code, when I hover over the second parameter (rows) passed to the constructor call, I see:

const rows: (string | number[])[][]

which looks like a two-dimensional array of the union of string and number[].

Could you provide a true minimal reproducible example which demonstrates the issue? Reproducing the issue in a standalone environment like the TypeScript Playground is a good way to know that we're all on the same page. As it stands, the type of rows in your code shows as (parameter) rows: [string, number[]][] in my IDE. Perhaps you are looking at the type of some variable you haven't included in the question? — jcalz
– jcalz, Commented Aug 21, 2019 at 18:06

Richard Haddad · Accepted Answer · 2019-08-21 22:51:10Z

2

An array of tuple, which have

a string as first element,
an array of number as second element

If I'm not wrong on what you're searching:

type MyTuple = [string, number[]];

const myArray: MyTuple[] = [
    ['str', [1, 2, 3]]
];

So your code seems OK, your issue concerns more VS code.

answered Aug 21, 2019 at 22:51

Richard Haddad

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1 Comment

user56reinstatemonica8 Over a year ago

I think the problem in the original code is that Array<labeledValuesType> takes a type (labeledValuesType) that is already an array, then wraps it in another Array<>?

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