app.js

var http = require('http');
var express = require('express');

var app = express();

app.set('view engine', 'jade');
app.set('views', __dirname + '/views');

app.locals.global = 'global';

app.use(function (req, res, next) {
  res.locals.local = 'local';
  next();
});

app.get('/', function (req, res, next) {
  res.render('index');
});

http.createServer(app).listen(3002);

index.js

-console.log(locals); // { [Function: locals] local: 'local' }