worker.js

let count = 0;

self.addEventListener('message',  e => {
	console.log('web worker is starting...')
    let { requestUrls } = e.data;

    const req = () => {
      fireRequest(requestUrls[count], token)
      .then((data) => {
        //posts to component to be store in db.
        postMessage({ data, key: requestUrls[count] })
        if( count < requestUrls.length -1) {
              count = count + 1;
              req();
          }
          else {
            //post message to component when done
            postMessage({ status: 'done' })
          }
         
      })
      .catch((err) => console.log('err:', err))
    }
    req();
    
})


function fireRequest(url, token) {
  return fetch(url, {
    headers: {
      'Content-Type': 'application/json'
    }
  })
  .then(res => res.json())
}