IndexedDB return value Deferred

Question

I have a small javascript project and I use indexedDB to store some values.The problem is that indexedDB is asynchronous and I cant return a value from request.onsuccess.:

function read(email) {
    var transaction = db.transaction(["usuario"]);
    var objectStore = transaction.objectStore("usuario");
    var request = objectStore.get(email);

    request.onerror = function (event) {
        console.log("No se pudieron sacar los datos de la base de datos!");
    };

    request.onsuccess = function (event) {
        if (request.result) {
            console.log(request.result);
        }

        else {
            console.log(email + " no se encontro en la BD!");
            return true;
        }
    };
}

I am trying to return the object stored by the key email.console.log prints out the object in the console but when return request.result is asigned it returns things of no use. I can see that there is a lot of qustions about asynchronous operations already in this site including Deffered function but considering my limited knowlege of javascript I cant seem to get the grasp of it so if anyone could please explain to me how do I return the found value .onsuccess

Hitesh Kumar · Accepted Answer · 2017-02-28T04:46:54.753

If you are using jQuery in your project then you can use deferred of jQuery. Jose on Code has a very good explanation of it.

function read(email) {
  var deferred = $.Deferred();
  var transaction = db.transaction(["usuario"]);
  var objectStore = transaction.objectStore("usuario");
  var request = objectStore.get(email);

  request.onerror = function(event) {
    console.log("No se pudieron sacar los datos de la base de datos!");
  };

  request.onsuccess = function(event) {
    if (request.result) {
      console.log(request.result);
      deferred.resolve(request.result);
    } else {
      console.log(email + " no se encontro en la BD!");
      return true;
    }
  };
  return deferred;
}


read(mail).done(function(value) {
  alert(value);
});

IndexedDB return value Deferred

1 Answers1