//Create new IndexedDB
var request = window.indexedDB.open("Offline-DB", 1);

//set variable storagedata to IndexedDB
request.onupgradeneeded = function(event) {
   var db = event.target.result;
   var transaction = event.target.transaction;
   var objectStore = db.createObjectStore("sig", {keyPath: 'key', autoIncrement: true});
   objectStore.add({value: storagedata});

   }