TypeScript error - property 'xyz' does not exist on type { }

Question

I have a simple JavaScript function (in a .tsx file)

export async function addDealer(payload: object) {
  let tempSupplierId = "cc9cfc30-5c01-11ec-bf63-0242ac130002"
  let addDealerURL = URLMap("addDealerAPI")
  addDealerURL = addDealerURL.replace("{supplierId}", tempSupplierId)
  let result = {}
  try {
    result.data = await fetch(addDealerURL, { //line 39
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(payload)
    })
  } catch (e) {
    result.error = e  //line 47
  }
  return result;
}

It gives compile errors like property 'data' does not exist on type '{}' and property 'error' does not exist on type '{}' due to lines 39 and 47. This is a valid code in plain JavaScript, but TypeScript won't allow because result - {}.

I understand these are valid errors and why they are appearing. I just don't know how to solve these.

I tried defining a type at the top of the file as below:

type resultType = {
  data: any;
  error: any;
}

And in the function, defined a result as resultType.

  let result: resultType

With this change I get new errors as:

Variable 'result' is used before being assigned.

I am confused with TypeScript, as I am still getting acquanted with it.