How to properly add index signature to object

Question

I have following errors (solution is working):

Element implicitly has an 'any' type because type '{}' has no index signature. [7017]

Code:

const createCollection = (jsonObject: object, namesObject: object): INameHex[] => {
  return Object.keys(jsonObject).map(itemKey => {
    return {
      name: namesObject[itemKey],
      hex: jsonObject[itemKey],
    }
  })
}

I tried adding interface instead of object (maybe incorrectly), something like - jsonObject: IProps. But it is not helping since my object (jsonObject argument) looks like that:

  success: string
  error: string
  [propName: string]: string

or

  default: string
  [propName: string]: string

so the object structure differs. So I would really like to know how to resolve no index signature error in this scenario?

Nurbol Alpysbayev · Accepted Answer · 2019-02-08T08:17:42.420

1

Does it look like what you want?

interface JSONObj {
    success: string
    error: string
    [propName: string]: string // this is an index signature 
}

interface NamesObj {
    default: string
    [propName: string]: string // this is an index signature
}

const createCollection = (jsonObject: JSONObj | NamesObj, namesObject: NamesObj): INameHex[] => {
    return Object.keys(jsonObject).map(itemKey => {
      return {
        name: namesObject[itemKey],
        hex: jsonObject[itemKey],
      }
    })
  }

It produces no errors and is perfectly correct from the types POV.

edited Feb 08 '19 at 08:17

answered Feb 08 '19 at 08:11

Nurbol Alpysbayev

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It is not a solution for this code since jsonObject can be of type JSONObj or NamesObj or 2 more different objects. They all have the same property [propName: string]: string – Marta Feb 08 '19 at 08:16
@Marta Then you just make it a union. See the updated answer. – Nurbol Alpysbayev Feb 08 '19 at 08:18
Yes - thank you, that is what I needed. Such an easy solution and I spent hours on that already – Marta Feb 08 '19 at 08:31
@Marta glad I could help! – Nurbol Alpysbayev Feb 08 '19 at 08:34

How to properly add index signature to object

1 Answers1