create a cache in javascript

In JavaScript, there are several ways to create a cache. One of the easiest is to use the browser's built-in local storage or session storage.

Using Local Storage


index.tsx
// Check if the user's browser supports localStorage
if (typeof(Storage) !== "undefined") {

  // Retrieve or create a cache
  var cache = localStorage.getItem("myCache");
  if (!cache) {
    cache = {};
    localStorage.setItem("myCache", JSON.stringify(cache));
  } else {
    cache = JSON.parse(cache);
  }

  // Add an item to the cache
  cache["myKey"] = "myValue";
  localStorage.setItem("myCache", JSON.stringify(cache));

} else {
  // No localStorage support, fall back to another solution
}
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In the above example, we first check if the user's browser supports local storage. If it does, we retrieve the cache from local storage or create a new one if it doesn't exist. We then add a key-value pair to the cache and save it back to local storage.

Local storage has a maximum size of around 5-10MB, depending on the browser.

Using Session Storage


index.tsx
// Check if the user's browser supports sessionStorage
if (typeof(Storage) !== "undefined") {

  // Retrieve or create a cache
  var cache = sessionStorage.getItem("myCache");
  if (!cache) {
    cache = {};
    sessionStorage.setItem("myCache", JSON.stringify(cache));
  } else {
    cache = JSON.parse(cache);
  }

  // Add an item to the cache
  cache["myKey"] = "myValue";
  sessionStorage.setItem("myCache", JSON.stringify(cache));

} else {
  // No sessionStorage support, fall back to another solution
}
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Session storage works similarly to local storage, but the data is cleared when the browser is closed or the tab is closed.

Using IndexedDB


index.tsx
// Check if the user's browser supports indexedDB
if (window.indexedDB) {

  // Open a connection to the cache database
  var request = indexedDB.open("myCacheDB", 1);

  // Handle database upgrade and creation
  request.onupgradeneeded = function(event) {
    var db = event.target.result;
    var cache = db.createObjectStore("myCache", {keyPath: "key"});
  };

  // Handle database opening
  request.onsuccess = function(event) {
    var db = event.target.result;

    // Retrieve or create a cache transaction
    var transaction = db.transaction(["myCache"], "readwrite");
    var cache = transaction.objectStore("myCache");

    // Add an item to the cache
    var item = {key: "myKey", value: "myValue"};
    cache.put(item);

    // Close the transaction and database connection
    transaction.oncomplete = function(event) {
      db.close();
    };
  };

} else {
  // No indexedDB support, fall back to another solution
}
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IndexedDB is a more powerful and flexible way to store data on the client-side, with larger storage space. In the above example, we first check if the user's browser supports indexedDB. We then open a connection to the cache database and create an object store to hold the cache. We retrieve or create a cache transaction and add a key-value pair to the cache. Finally, we close the transaction and the database connection.

Note that the above examples are simplified for illustration purposes and you may need to handle errors, parsing, and serializing of data, as well as setting expiration times or clearing old items from the cache.

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