Node.js + Express: Save the user and password in the browser

I'm learning Node.JS with Express, now I'm working in the login form, all is right but when I login, the browser never save my Username and Password. How can I do it?

My App configuration for SESSION is this

app.use(express.bodyParser());
app.use(express.cookieParser());
app.use(express.session({ key: 'session', secret: 'log', store: new express.session.MemoryStore }));

Then I use the req.body.username and req.body.password to authenticate. Finally I save de ID SESSION in req.session.user_id.

Thanks for the help. I don't know if is safe to save this things in the browser, but I'm thinking in the user.