Typescript check propery for unknow type - node.js

Question

I have an api request and for error statement. I want to return message from payload.
But message object can change depending on error. For example, payload object can be
{ message: 'Not Authorized', type: 'service.not_authorized' }
or
{
"errors": [
{
"category": "AUTHENTICATION_ERROR",
"code": "UNAUTHORIZED",
"detail": "Authorization code is expired.
}
]
}
I can't create interfaces for all possible payloads.
In JS, basically I can write this :
if(payload && payload.message){
return payload.message
}
if(payload && payload.errors){
const message = payload.errors.length>0 ? payload.errors[0].detail : 'Error'
return message;
}
Now I can try to do this with Typescript
import axios from "axios";
interface IApiError{
category:string,
code:string,
detail:string
}
const CustomError=<T>(e:T):string=>{
let message="";
if(axios.isAxiosError(e)){
const payload = e.response?.data; // payload:unknown
if(payload){
if(typeof payload === 'object'){
if(payload.hasOwnProperty('message')){
message=payload.message;
// Error : Property 'message' does not exist on type 'object'.
}
else if(payload.hasOwnProperty('errors')){
const errorsArray:IApiError[]=payload.errors;
message=errorsArray[0].detail;
// Error : Property 'errors' does not exist on type 'object'.
}
}
}
}
return message;
}
How can I solve this?
Edit
I found this topic. But according this we should create interfaces and typeguard for every possible payload option.

Answer 1

I guess, I found a solution. Based on this answer I created a function.
// Basically it takes 3 arguments
// o -> Object that we don't know what is look like
// prop -> The name of prop that we are looking for
// type -> A variable with the same type with our prop
// Because I didn't find to send type to method in typescript
// (for example string,number,boolean)
const getProp = (o: unknown, prop: string, type:any): any => {
// Checks whether the object contains the requested prop
const p = (o as any)[prop]
// If this field instance of requested type
if (typeof p === typeof type) {
return p;
}
return undefined;
}
Let's test this for different scenarios.
let obj:unknown={ message: 'Not Authorized', type: 'service.not_authorized' }
let obj2:unknown={
"errors": [
{
"category": "AUTHENTICATION_ERROR",
"code": "UNAUTHORIZED",
"detail": "Authorization code is expired."
}
]
}
// In first object I looking for message field and it should be string
let res=getProp(obj,"message","");
res ? console.log(res) : console.log("Not Found");
// console result -> Not Authorized
// In second object I'm intentionally sending the wrong type
// There is a field with name 'errors' but it's type is array
res=getProp(obj2,"errors","");
res && res.length>0 ? console.log(res) : console.log("Not Found");
// console result -> Not Found
// I send true types
res=getProp(obj2,"errors",[]);
res && res.length>0 ? console.log(res[0].detail) : console.log("Not Found");
// console result -> Authorization code is expired.