Defining an array of string to string map in typescript [duplicate]

Question

I have an interface that accepts { [key:string]: string }. I want to test several cases for it. For this I want to define an array containing my test cases as follows:

const tests: [ {[key: string]: string} ] = [{
  "A": "B"
}, {
  "C": "D"
}]

But it will not compile because Typescript is assuming those inline objects are types in of themselves.

Type '[{ A: string; }, { C: string; }]' is not assignable to type '[{ [key: string]: string; }]'. Source has 2 element(s) but target allows only 1.

Array<{[key: string]: string}> should also work. The problem is that your declaration only allows one element inside of the array, yet you pass 2 elements into it. — user13258211
– user13258211, Commented Apr 26, 2022 at 7:41

Kaspar Etter · Accepted Answer · 2022-04-26 07:43:14Z

1

This is not how you type arrays of a particular type in TypeScript. The following gives no errors in the playground:

const tests: {[key: string]: string}[] = [{
  "A": "B"
}, {
  "C": "D"
}]

edited Apr 26, 2022 at 7:43

answered Apr 26, 2022 at 7:41

Kaspar Etter

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2 Comments

user13258211 Over a year ago

[ {[key: string]: string} ] is definitely an Array, but only with one element inside of it ;)

VLAZ Over a year ago

@MikeS. TS calls that a tuple. Yes, it accepts an array for it but the type itself has a distinct name.

Solivar · Accepted Answer · 2022-04-26 07:43:34Z

1

It should be like this:

const tests: {[key: string]: string}[] = [{
  "A": "B"
}, {
  "C": "D"
}]

Doing it like you did, [{[key: string]: string}], means it should be an array with one object inside.

answered Apr 26, 2022 at 7:43

Solivar

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