CODEWITHSUNDEEP
typescript
Jatin Sanghvi
Jatin Sanghvi

Reputation: 2243

Initialize Map in TypeScript with dynamic values

Is it possible to initialize the ReadOnlyMap with values generated during runtime in TypeScript? The Map can be initialized if the array is provided as part of constructing the Map, but fails if the array is passed to it by means of a variable. Please see the code below.

// Works.
let X: ReadonlyMap<number, number> = new Map([
    [0, 0],
    [1, 1],
]);

let Y = [
    [0, 0],
    [1, 1],
];

// Does not work.
// Argument of type 'number[][]' is not assignable to parameter of type 'ReadonlyArray<[number, number]>'.
// Type 'number[]' is missing the following properties from type '[number, number]': 0, 1
let Z: ReadonlyMap<number, number> = new Map(Y);

Is there another way available to construct the Map in a single statement? I will like to avoid newing up an empty Map, call set() for each value and then copying its reference to ReadonlyMap.

Upvotes: 1

Views: 5317

Answers (1)

Jan Wendland
Jan Wendland

Reputation: 1430

Have you tried explicit typing of your input array? For example:

const Y: ReadonlyArray<[number, number]> = [
  [0, 0],
  [1, 1],
];


const Z: ReadonlyMap<number, number> = new Map<number, number>(Y);

Upvotes: 1

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