IndexedDB upgrade code to add index to an existing object store

idb.js

  request.onupgradeneeded = function(event) {
    var db = event.target.result;
    var upgradeTransaction = event.target.transaction;
    var objectStore;
    if (!db.objectStoreNames.contains("my-store")) {
      objectStore = db.createObjectStore("my-store");
    } else {
      objectStore = upgradeTransaction.objectStore('my-store');
    }

    if (!objectStore.indexNames.contains("my-index")) {
      objectStore.createIndex("my-index", "status", { unique: false });
    }
  };