Fetch API & Handling JSON Responses

async function fetchWithProgress(url, onProgress) {
  const response = await fetch(url);
  const reader = response.body.getReader();
  const contentLength = +response.headers.get('Content-Length');
  
  let receivedLength = 0;
  while(true) {
    const {done, value} = await reader.read();
    if (done) break;
    
    receivedLength += value.length;
    onProgress(receivedLength / contentLength);
  }
}