ExtJS 6: JSON Web Token API Login with Promises

Firewall.js

Ext.define('App.security.Firewall', {
    singleton: true,
    requires: [
        'App.security.TokenStorage'
    ],

    isLoggedIn: function() {
        return null !== App.security.TokenStorage.retrieve();
    },

    login: function(username, password) {
        var deferred = new Ext.Deferred();

        Ext.Ajax.request({
            url: App.server.Router.generate('authenticate'),
            method: 'POST',
            jsonData: {
                'username': username,
                'password': password
            },

            success: function (response) {
                var data = Ext.decode(response.responseText);
                if (data.token) {
                    App.security.TokenStorage.save(data.token);

                    deferred.resolve(data, response);
                } else {
                    deferred.reject(data, response);
                }
            },

            failure: function (response) {
                var data = Ext.decode(response.responseText);

                App.security.TokenStorage.clear();

                deferred.reject(data, response);
            }
        });

        return deferred.promise;
    },

    logout: function(callback) {
        App.security.TokenStorage.clear();

        // The "old" way of using callbacks. You can easily rewrite this using Promise, too, see login method.
        callback();
    }
}, function () {
    Ext.Ajax.on('beforerequest', function(conn, options) {
        if (App.security.Firewall.isLoggedIn()) {
            options.headers = options.headers || {};
            options.headers['Authorization'] = 'Bearer ' + App.security.TokenStorage.retrieve();
        }
    });
});

LoginController.js

Ext.define('App.view.login.LoginController', {
    extend: 'Ext.app.ViewController',
    alias: 'controller.login',

    onLoginClick: function() {
        var data = this.getView().down('form').getValues();

        App.security.Firewall.login(data.username, data.password).then(function() {
            this.getView().destroy();

            Ext.create({
                xtype: 'app-main'
            });
        }.bind(this), function(data) {
            Ext.Msg.alert('Error', data.message || 'An error occurred while logging in.');
        });
    }
});

TokenStorage.js

Ext.define('App.security.TokenStorage', {
    singleton: true,
    storageKey: 'json-web-token',

    clear: function () {
        localStorage.removeItem(this.storageKey);
    },

    retrieve: function() {
        return localStorage.getItem(this.storageKey);
    },

    save: function (token) {
        localStorage.setItem(this.storageKey, token);
    }
});