How to use the express-validator function in express-validator

var app = express(opts)
var server

// Instantiate Singleton Manager (which lists all blog files)
Manager.instance.init()
app.set('config', config.getConfigByWebsite())

app.use(flash())
app.use(cookieParser())
app.use(passport.initialize())
app.use(passport.session())
app.use(
  bodyParser.urlencoded({limit: '1gb', extended: true, parameterLimit: 50000})
)
app.use(expressValidator())
app.use(csrf({cookie: {secure: config.cookie.secure}}))
app.use(function(req, res, next) {
  if (req.url.indexOf('/abe/') > -1) {
    res.locals._csrf = req.csrfToken()
  }
  next()
})

app.use(bodyParser.json({limit: '1gb'}))

if (config.security === true) {
  app.use(helmet())
  app.use(
    helmet.csp({
      directives: {
        defaultSrc: ["'self'"],

const server = http.createServer(app);
const port = process.env.PORT || 3030;

// Hey you! care about my order http://stackoverflow.com/a/16781554/2034015

// Databases.
initializeMongodb();
const dbSession = initializeRedis(Session);

// Cookies.
app.use(cookieParser());

// Body.
app.use(bodyParser.urlencoded({extended: false}));
app.use(bodyParser.json());
app.use(expressValidator({
  customValidators: {
    isSlug: function (input) {
      if (typeof input !== 'string' ||
          input.length < 5 || input.length > 55) return false;

      const re = /^[a-zA-Z0-9_-]+$/;
      return input.match(re);
    }
  }
}));

// Session.
const session = Session({
  resave: true,
  saveUninitialized: true,
  key: config.get('session.key'),

// Logging information in the console
app.use(morgan('dev'));

// Request body parser
app.use(bodyParser.urlencoded({extended: false}));
app.use(bodyParser.json());
app.use(cors());

// Attach helpers to request
app.use((req, res, next) => {
    req.helpers = helpers;
    next();
});

// Attach express validator to requests
app.use(expressValidator());

// Routes
app.use('/', routes);

// Handle Errors
app.use(errorHandlers.notFound);

app.use(errorHandlers.showErrors);

export default app;

public initalize(app) {

    // view engine setup
    app.set('views', path.join(__dirname, 'views'));
    app.set('view engine', 'ejs');

    // validator
    app.use(expressValidator());

    // favicon
    let faviconPath = path.join(__dirname, '.', 'public', 'favicon.ico');
    app.use(favicon(faviconPath)); // uncomment after placing your favicon in /public

    // logger
    app.use(morgan('dev'));

    // bodyParser
    app.use(bodyParser.json());
    app.use(bodyParser.urlencoded({ extended: false }));

    // cookieParser
    app.use(cookieParser());

    // i18n localication

}),
  );
  // parse anything else
  app.use(bodyParser.raw({ limit: '20mb' }));
  app.use(
    methodOverride((req, res) => {
      if (req.body && typeof req.body === 'object' && '_method' in req.body) {
        // look in urlencoded POST bodies and delete it
        const method = req.body._method;
        delete req.body._method;
        return method;
      }
    }),
  );
  // must be right after bodyParser
  app.use(expressValidator());
  app.use(
    busboy({
      limits: {
        fileSize: 5242880,
      },
    }),
  );
  app.use(hpp());
  if (process.env.NODE_ENV !== 'production') {
    expressWinston.requestWhitelist.push('body');
    expressWinston.responseWhitelist.push('body');
    app.use(
      expressWinston.logger({
        winstonInstance,
        meta: true,
        msg: 'HTTP {{req.method}} {{req.url}} {{res.statusCode}} {{res.responseTime}}ms',

private config(): void {
		this.app.use(bodyParser.json());
		this.app.use(bodyParser.urlencoded({ extended: false }));
		this.app.use(cors());
		this.app.use(compression());
		this.app.use(expressValidator());

		this.routes.routes(this.app);

		if (AppConfig.NODE_ENV === "production") {
			// Serve any static files
			this.app.use(express.static(AppConfig.UI_DIR));

			// Handle React routing, return all requests to React app
			this.app.get("*", (req, res) => {
				res.sendFile(path.join(AppConfig.UI_DIR, "index.html"));
			});
		}
	}
}

app.set('views', path.join(__dirname, 'views'));

  app.use(function (req, res, next) {
    res.header('Access-Control-Allow-Origin', '*');
    res.header('Access-Control-Allow-Headers', 'Cache-Control, Pragma, Origin, Authorization, Content-Type, X-Requested-With, access-token');
    res.header('Access-Control-Allow-Methods', 'GET, PUT, POST, DELETE');
    if ('OPTIONS' === req.method) {
      res.status(204).send();
    }
    else {
      next();
    }
  });

  app.use(bodyParser.json());
  app.use(expressValidator({
    customValidators: customValidators,
    customSanitizers : customSanitizers
  }));

  app.use(validationGroups());
  app.set('config', config);
  app.set('models', models);
  app.set('port', config.port);
  app.set('logger', logger);
  app.set('actions', actions);
  app.set('emailSender', emailSender);

  app.use(morgan('combined',{
    stream: {
      write: (message) => {
        logger.info(message);

setupMiddlewareValidator_() {
    this.getServer()
      .getEngine()
      .use(
        expressValidator({
          customValidators: {
            custom: function(value, fn) {
              return fn(value);
            },
          },
          errorFormatter: (param, msg, value) => {
            return {
              reason: msg,
              context: {
                param: param,
                value: value,
              },
            };
          },
        })
      );

return;
    }
    if (ALLOW_ORIGIN.indexOf(origin) !== -1 || origin === undefined) {
      callback(null, true);
    } else {
      callback(new Error('not allowed by CORS'));
    }
  },
  credentials: true,
}));

app.use(morgan(ENVIRONMENT === 'production' ? 'combined' : 'dev'));
app.use(compression());
app.use(bodyParser.json({ limit: '50mb' }));
app.use(bodyParser.urlencoded({ extended: true }));
app.use(expressValidator());
app.use(session({
  resave: true,
  saveUninitialized: true,
  secret: SESSION_SECRET,
  store: sessionStore(),
  cookie: { maxAge: 24 * 60 * 60 * 1000 },
}));
app.use(passport.initialize());
app.use(passport.session());
app.use(lusca.xframe('SAMEORIGIN'));
app.use(lusca.xssProtection(true));

userApi(app);
diagramApi(app);
datasetApi(app);
flowsenseApi(app);