28. API Cache - Fallback

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HTML

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<div id="app">
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</div>

JavaScript

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/* In today’s project, we’re going to modify our API cache script
to fallback to the cache if the API call fails—even if data has expired.
Showing something, even if it’s a bit out of date, is better than showing nothing at all.*/

const appOutput = document.querySelector('#app');
let storageID;
var numberOfArticles = 2;
const sanitizeHTML = function (str) {
  return str.replace(/[^\w. ]/gi, function (c) {
    return '&#' + c.charCodeAt(0) + ';';
  })
};
const isDataValid = function (saved, expirationDate) {
  if (!saved || !saved.data || !saved.timestamp) return false;
  const difference = new Date().getTime() - saved.timestamp;
  return difference < expirationDate;
}
const saveData = function (data) {
  const cache = {
    data: data,
    timestamp: new Date().getTime()
  }
  localStorage.setItem(storageID, JSON.stringify(cache));
}
const getData = function () {
  const saved = JSON.parse(localStorage.getItem(storageID));
  if (!saved) return;
  if (isDataValid(saved, 1000 * 10)) {
    return saved.data;
  }
}
const render = function (articles) {
  appOutput.innerHTML = '<h3 class="category">Pirate articles:</h3>' + articles.map(function (article) {
    return (`
        <div class="container">
          <ul class="title">
            <li> <strong>Title:</strong> ${sanitizeHTML(article.title)}</li>
            <li> <strong>Author:</strong> ${sanitizeHTML(article.author)}</li>
            <li> <strong>Publication date:</strong> ${sanitizeHTML(article.pubdate)}</li>
          </ul>
          <div class="article"><p>${sanitizeHTML(article.article)}</p></div>
        </div>
        <hr>
        <br>
        `);
  }).join('');
}
const getFirstFewArticles = function (articles) {
  return articles.slice(0, numberOfArticles);
}
const getNews = function () {
  // Check for valid cached data,
  // If exist, use it
  const saved = getData();
  if (saved) {
    render(saved);
    console.log("Loaded from cache");
    return;
  }
  fetch('https://vanillajsacademy.com/api/pirates.json').then(function (response) {
    if (response.ok) {
      return response.json();
    } else {
      return Promise.reject(response);
    }
  }).then(function (data) {
    const articles = getFirstFewArticles(data.articles);
    saveData(articles);
    render(articles);
    console.log("Fetched from API");
  }).catch(function (error) {
    console.log("something went wrong", error);
    appOutput.textContent = "Something went wrong...";
  })
}
getNews();