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I'm fighting with property success which is definited in API (recaptcha).

* The structure of response from the veirfy API is * "success": true|false, * "challenge_ts": timestamp, // timestamp of the challenge load (ISO format yyyy-MM-dd'T'HH:mm:ssZZ) * "hostname": string, // the hostname of the site where the reCAPTCHA was solved * "error-codes": [...] // optional

Below I tried use optional chaining to fix that problem, but it does not work. I have tried use interface on different sides, but I can't fix that again with it.

Below code:

import fetch from "node-fetch"
//...
try {
const response = await fetch(
  `https://www.google.com/recaptcha/api/siteverify?secret=${process.env.GOOGLE_RECAPTCHA_SECRETKEY}&response=${captcha}`,
    headers: {
      "Content-Type": "application/x-www-form-urlencoded; charset=utf-8",
    method: "POST",
const captchaValidation = await response.json();
if(captchaValidation?.success) // error: Property 'success' does not exist on type '{}'
} catch (error) {}
How can I get access to that property?
                That's a typescript error. You have to tell TypeScript what "type" captchaValidation has, and therefor what properties are available.
– Andreas
                Oct 6, 2022 at 8:32
                I know that, but I have not idea how to implement that "type" to captchaValidation :/ Need help
– DonEmil
                Oct 6, 2022 at 8:42
It seem shat .json is not type aware and it returns Promis<never< - .json method
I can propose a solution you need to delcare the Captcha types and tell typescript believe me it is this type
export interface CaptchaResponse {
  success: boolean;
  challenge_ts: string;
  hostname: string;     
  error-codes?: any[];
const rawResponse = await response.json();
// next line is nothing more just saying - believe me it is this type. It will not do type checking
const typedRespone = rawResponse as CaptchaResponse;
if(typedRespone.success)
You can create an interface and declare that the response is that interface. Then TypeScript is told that a success property should exist.
export interface ApiResponse {
  success: boolean;
  challenge_ts: string;
  hostname: string;     
  error-codes?: any[];
Then declare it as that type:
const captchaValidation: ApiResponse = await response.json();
                According to your second option I have got an error: Type 'unknown' is not assignable to type 'ApiResponse'.  The first option also throw an error: Type 'Response' is missing the following properties from type 'ApiResponse': success, challenge_ts, hostname
– DonEmil
                Oct 6, 2022 at 8:55
                Yeah wasn't sure which one should return your desired object, never mind the first line then. Seems TypeScript already knows your await response.json() returns unknown so then you could do type-casting like the other answer suggests.
– CoderApprentice
                Oct 6, 2022 at 9:05
        
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