Function isJsonResponse

isJsonResponse(response: unknown): response is Response

Type guard to validate if a Response object contains JSON content. Checks both the Content-Type header and ensures it's a valid Response object.

Parameters

response: unknown
The Response object to validate

Returns response is Response

Type predicate indicating if the response contains JSON content

Example

// Valid JSON response
const jsonResponse = new Response('{"data": "test"}', {
  headers: { 'Content-Type': 'application/json' }
});
if (isJsonResponse(jsonResponse)) {
  const data = await jsonResponse.json();
  console.log('JSON data:', data);
}

// Non-JSON response
const htmlResponse = new Response('<html>...</html>', {
  headers: { 'Content-Type': 'text/html' }
});
if (!isJsonResponse(htmlResponse)) {
  console.log('Not a JSON response');
}

Source

export function isJsonResponse(response: unknown): response is Response {
  if (!isHttpResponse(response)) {
    return false;
  }
  const contentType = response.headers.get("Content-Type");
  return (
    contentType !== null && (contentType.includes("/json") || contentType.includes("/javascript"))
  );
}