IndexedDB.js

var DBNAME = 'tabgrenade';
var DBVERSION = 1;
var STORENAME = 'keyvaluepairs';
var db = null;

function withStore(type, f) {
  if (db) {
    f(db.transaction(STORENAME, type).objectStore(STORENAME));
  } else {
    var openreq = indexedDB.open(DBNAME, DBVERSION);
    openreq.onerror = function withStoreOnError() {
      console.error("asyncStorage: can't open database:", openreq.error.name);
    };
    openreq.onupgradeneeded = function withStoreOnUpgradeNeeded() {
      // First time setup: create an empty object store
      openreq.result.createObjectStore(STORENAME);
    };
    openreq.onsuccess = function withStoreOnSuccess() {
      db = openreq.result;
      f(db.transaction(STORENAME, type).objectStore(STORENAME));
    };
  }
}