This is just the beginning of the native storage promise system

MyStorageEvent.js

Storage.prototype._setItem = Storage.prototype.setItem;

Storage.prototype.setItem = function(key, value, type, name) {

    var eventName = name || 'storage';
    var eventObject = {
        "target": window,
        "type": "storage",
        "bubbles": false,
        "cancelable": false,
        "key": key,
        "oldValue": type.getItem(key),
        "newValue": value,
        "url": window.location.href,
        "storageArea": type
    };

    this._setItem(key, value);
    window.dispatchEvent(new StorageEvent(eventName, eventObject));
};

window.addEventListener('storage', function(e){ document.querySelector('body').innerHTML = e.newValue;});