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                const cachedFetch = (url, options) => {
  // Use the URL as the cache key to sessionStorage
  let cacheKey = url
  return fetch(url, options).then(response => {
    // let's only store in cache if the content-type is 
    // JSON or something non-binary
    if (response.status === 200) {
      let ct = response.headers.get('Content-Type')
      if (ct && (ct.match(/application\/json/i) || ct.match(/text\//i))) {
        // There is a .json() instead of .text() but 
        // we're going to store it in sessionStorage as 
        // string anyway.
        // If we don't clone the response, it will be 
        // consumed by the time it's returned. This 
        // way we're being un-intrusive. 
        response.clone().text().then(content => {
          sessionStorage.setItem(cacheKey, content)
    return response

  .then(r => r.json())
  .then(info => {
    console.log('Your origin is ' + info.origin)

  .then(r => r.text())
  .then(document => {
    console.log('Document has ' + document.match(/<p>/).length + ' paragraphs')

  .then(r => r.blob())
  .then(image => {
    console.log('Image is ' + image.size + ' bytes')