TypeScript compiler error: an index signature with a parameter of type 'number' is missing on an empty object

Can someone help me with reversing the key-value pair of an object that contains a nested object value? My code works fine in plain JavaScript, but I'm encountering a compile error when using TypeScript.

The error message states:

Element implicitly has an 'any' type because expression of type 'number' can't be used to index type '{}'. No index signature with a parameter of type 'number' was found on type '{}'.

I would appreciate any advice or suggestions on how to resolve this issue.

Typescriplt playground link

Expected Output:

{
  "5": "dataCut-1",
  "7": "dataCut-2",
  "8": "dataCut-3",
  "12": "dataCut-4",
  "15": "dataCut-5",
  "16": "dataCut-6",
  "undefined": "dataCut-7"
}
typescriptobject

Answer №1

It was pointed out in the comment that you need to provide more annotations.

I would like to emphasize that using ! to silence type checking is not recommended. The warning is there for a reason, as it alerts you to the possibility of encountering an undefined key, which is explicitly allowed by your interface and exists in your dataset.

Your output will contain undefined: 'dataCut-7'

The code snippet below filters out entries without an id, but feel free to handle them in any way you see fit, as long as they are addressed.

Object.entries(data).reduce((acc:Record<string, string>, [key, value]) => {
    if(value.id) acc[value.id] = key;
    return acc
}, {});

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