scratch_25.js

(function showIndexedDbSize() {
  "use strict";
  var db;
  var storesizes = new Array();

  function openDatabase() {
    return new Promise(function(resolve, reject) {
      //prompt for DB name
      var dbname = prompt('Please enter your Database Name', '');

      if (dbname !== null) {
        var request = window.indexedDB.open(dbname);
        request.onsuccess = function (event) {
          db = event.target.result;
          resolve(db.objectStoreNames);
        };
      }

    });
  }

  function getObjectStoreData(storename) {
    return new Promise(function(resolve, reject) {
      var trans = db.transaction(storename, IDBTransaction.READ_ONLY);
      var store = trans.objectStore(storename);
      var items = [];
      trans.oncomplete = function(evt) {
        var szBytes = toSize(items);
        var szMBytes = (szBytes / 1024 / 1024).toFixed(2);
        storesizes.push({'Store Name': storename, 'Items': items.length,  'Size': szMBytes + 'MB (' + szBytes + ' bytes)'});
        resolve();
      };
      var cursorRequest = store.openCursor();
      cursorRequest.onerror = function(error) {
        reject(error);
      };
      cursorRequest.onsuccess = function(evt) {
        var cursor = evt.target.result;
        if (cursor) {
          items.push(cursor.value);
          cursor.continue();
        }
      }
    });
  }

  function toSize(items) {
    var size = 0;
    console.log(JSON.stringify(items.slice(1500,1505)));

    for (var i = 0; i < items.length; i++) {
      var objectSize = JSON.stringify(items[i]).length;
      size += objectSize * 2;
    }
    return size;
  }

  openDatabase().then(function(stores) {
    var PromiseArray = [];
    for (var i=0; i < stores.length; i++) {
      PromiseArray.push(getObjectStoreData(stores[i]));
    }
    Promise.all(PromiseArray).then(function() {
      console.table(storesizes);
    });
  });
}());