title: What is NODE_ENV and how to use it in Express?
body: <p>This is my app that I'm currently running on production.</p>
  <pre><code>var app = express();
  app.set('views',settings.c.WEB_PATH + '/public/templates');
  app.set('view engine','ejs');
  app.configure(function(){
      app.use(express.favicon());
      app.use(express.static(settings.c.WEB_PATH + '/public'));
      app.use(express.bodyParser());
      app.use(express.cookieParser());
      app.use(express.methodOverride());
      app.use(express.session({
              cookie:{ domain:&quot;.&quot;+settings.c.SITE_DOMAIN, maxAge:1440009999},
              secret:'hamster',
              store: r_store,
              }));
      app.use(useragent.express());
      app.use(flash());
      app.use(passport.initialize());
      app.use(passport.session());
  });
  </code></pre>
  <p>Now I've learned about <code>NODE_ENV</code> and want to use it. How can I do this?</p>