typescript Cannot add headers to a fetch api using react-native

Can you try typing it as HeadersInit?

const requestHeaders: HeadersInit = new Headers();
requestHeaders.set('Content-Type', 'application/json');

const responseLogin = await fetch('URL', {
  method: 'POST',
  headers: requestHeaders,
  body: requestBody
});

If not, can you show the error you are getting when you are initiating it with the Headers() constructor, you showed in the question?