How to download files on WebExtension

download.js

// Use an A tag
// Firefox: OK, Chrome: NG
// Waiting with setTimeout is dirty

const downloadWithATag = (filename, text) => {
  const blob = new Blob([text], {type: 'text/plain;charset=utf-8'});
  const url = URL.createObjectURL(blob);
  
  const a = document.createElement('a');
  a.href = url;
  a.download = filename;
  Object.assign(a.style, {
    visibility: 'hidden',
    width: 0,
    height: 0,
    overflow: 'hidden',
    position: 'absolute'
  });
  document.body.appendChild(a);

  a.click();
  setTimeout(() => {
    document.body.removeChild(a);
    URL.revokeObjectURL(url);
  }, 10000); // <= dirty!
};


// Use browser.downloads API (requires "downloads" permission)
// Firefox: OK, Chrome: OK
// Either way it is dirty

let handlers = []; // Array<{id: string, url: string}>

browser.downloads.onChanged.addListener((delta) => {
  const handler = hanlders.find(h => h.id === delta.id);
  if (hanlder && delta.state) {
    if (delta.state.current === 'complete' || delta.state.current === 'interrupted') {
      URL.revokeObjectURL(handler.url);
      handlers = handlers.filter(h => h.id !== handler.id);
    }
  }
});

const downloadWithBrowserAPI = (filename, text) => {
  const text = 'sample text';
  const blob = new Blob([text], {type: 'text/plain;charset=utf-8'});
  const url = URL.createObjectURL(blob);
  browser.downloads.download({filename, url}, (id) => {
    handlers.push({id, url});
  });
};

// Is revokeObjectURL really necessary?