Measure total size of all indexeddb objects

totalIndexedDbSize.js

// forked from 
// https://github.com/jonnysmith1981/getIndexedDbSize

function showIndexedDbSize(dbname) {
    "use strict";
    var db;
    var totalSize = 0
   
    function openDatabase(dbname) {
      return new Promise(function(resolve, reject) {  
        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) {
          totalSize += toSize(items)
          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;
      for (var i = 0; i < items.length; i++) {
          var objectSize = JSON.stringify(items[i]).length;
          // why times two?
          size += objectSize * 2;
      }
      return size;
    }
   
    return openDatabase(dbname).then(function(stores) {
      var PromiseArray = [];
      for (var i=0; i < stores.length; i++) {
        PromiseArray.push(getObjectStoreData(stores[i]));    
      }
      return Promise.all(PromiseArray).then(function() {
         return totalSize
      });
    });
  }

  indexedDB.databases().then(dbs=>dbs.map(db=>db.name)).then(dbnames=>dbnames.map(showIndexedDbSize)).then(v=>Promise.all(v)).then(sizes=>sizes.reduce(function(x,y){return x+y})).then(console.log)