TypeScript type for object of objects?

Question

What would be the correct typescript type of something like

const test: MyType = {
  foo: { value: 1 },
  bar: { value: 2 }
}

something like

type MyType {
  [key: any]: {
    value:number
  }
}

results in

Object literal may only specify known properties, and 'foo' does not exist in type

Your question doesn't seem right, your type signature is not declared properly and would actually give you An index signature parameter type must be either 'string' or 'number' error even if it was declared properly. — yi fan song
– yi fan song, Commented Nov 30, 2020 at 19:12

pzaenger · Accepted Answer · 2020-11-30 18:41:25Z

3

An index signature parameter type must be either string or number:

type MyType = {
    [key: string]: { value: number; };
};

const test: MyType = {
    foo: { value: 1 },
    bar: { value: 2 }
};

Or, using Record:

const test: Record<string, { value: number }> = {
    foo: { value: 1 },
    bar: { value: 2 }
}

const test: Record<'foo' | 'bar', { value: number }> = {
    foo: { value: 1 },
    bar: { value: 2 }
}

answered Nov 30, 2020 at 18:41

pzaenger

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Comments

abhishek khandait · Accepted Answer · 2020-11-30 18:41:33Z

1

const test: Record<string, {value: number}> = {
    foo: { value: 1 },
    bar: { value: 2 }
};

answered Nov 30, 2020 at 18:41

abhishek khandait

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1 Comment

yi fan song Over a year ago

You could add some more info explaining why a record should be used instead of a type.

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