Typescript: Help defining a type for an Array of Arrays?

Question

I'm working with a legacy variable defined quite some time ago.

export const constellationNancyRomanTable = [
  [0.0000,24.0000,88.0000,'UMi'],
  [8.0000,14.5000,86.5000,'UMi'],
  [21.0000,23.0000,86.1667,'UMi'],
  [18.0000,21.0000,86.0000,'UMi'],
  ...
]

However, I'm very new to Typescript - so I'm half thinking of porting this variable to a new object based syntax as I understand type definitions for objects, but this array of arrays is alluding me. However, I was wondering how to define such a type / interface?

I'm thinking something along this line:

export interface ConstellationNancyRoman = Array<Array<[number, number, number, string]>>

Is somewhat correct?

Why not try it out? Right now that's not even a syntactically valid interface, looks like you've confused it with a type. — jonrsharpe
– jonrsharpe, Commented Jul 12, 2021 at 11:23

Terry · Accepted Answer · 2021-07-12 11:23:26Z

3

You're almost there: you have simply nested it one Array to deep, since you're defining your tuples already. This should work (use type not interface):

export type ConstellationNancyRoman = Array<[number, number, number, string]>;

See example on TypeScript playground.

You can use bracket notation all the way, even though for some people it might not be as readable as before:

export type ConstellationNancyRoman = [number, number, number, string][];

answered Jul 12, 2021 at 11:23

Terry

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1 Comment

Micheal J. Roberts Over a year ago

Hi Terry, ahhh simple - thank you for helping with this!

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