Why am I getting warnings about a TypeScript multidimensional array that works?

Question

I have an array of people stored in a multidimensional associative array. Each person belongs to a place and each place belongs to a timezone. I set up my variable like this:

interface AssociativeArray {
    [key: string]: Array<object> | string | number | object;
}

export var mapDB: AssociativeArray[] = [
    {
        timeZone: "HST",
        places: [
            {
                place: "Oahu",
                members: ["Frank", "Jerry", "Pearl"],
            },
            {
                place: "Maui",
                members: ["Susan", "Liana", "Bertha"],
            },
        ],
    },
    {
        timeZone: "PST",
        places: [
            {
                place: "Tahiti",
                members: ["Fido", "Snowy", "Butch"],
            },
        ],
    },
];

To access a specific element in the array, I use the following code:

console.log("The name: ", mapDB[0]["places"][1]["members"][2]);

This code returns the expected value of "Bertha". However, in VS Code, this line is marked with an error message:

Element implicitly has an 'any' type because expression of type '1' can't be used to index type 'string | number | object | object[]'.
  Property '1' does not exist on type 'string | number | object | object[]'

I have tried to write different versions of the "interface" but I cannot seem to get rid of the error message. Can someone help me fix it?

You'll get the best type for that value without using an explicit type annotation — Aluan Haddad
– Aluan Haddad, Commented Jun 16, 2023 at 6:11

Clarity · Accepted Answer · 2023-06-16 05:37:16Z

2

The error happens because TypeScript cannot infer the actual types of the nested elements in the multidimensional associative array. You need to be more specific with the types:

interface Place {
  place: string;
  members: string[];
}

interface TimeZone {
  timeZone: string;
  places: Place[];
}

export const mapDB: TimeZone[] = [
  {
    timeZone: "HST",
    places: [
      {
        place: "Oahu",
        members: ["Frank", "Jerry", "Pearl"],
      },
      {
        place: "Maui",
        members: ["Susan", "Liana", "Bertha"],
      },
    ],
  },
  {
    timeZone: "PST",
    places: [
      {
        place: "Tahiti",
        members: ["Fido", "Snowy", "Butch"],
      },
    ],
  },
];

answered Jun 16, 2023 at 5:37

Clarity

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