Running Node JS app in localhost/contextname

Question

I am having one node JS application ,its always running in localhost but i want to run it on localhost/sometext(context).How can i achieve this?

 var express = require('express');
    var api = require('./api/api');
    var http = require('http');
    var path = require('path');
    var app = express();

    var allowCrossDomain = function(req, res, next) {
        res.header('Access-Control-Allow-Origin', config.allowedDomains);
        res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');
        res.header('Access-Control-Allow-Headers', 'Content-Type');
        next();
    }
    // all environments
    app.set('port', process.env.PORT || 80);
    app.set('views', path.join(__dirname, 'views'));
    app.use(express.favicon());
    app.use(express.logger('dev'));
    app.use(express.json());
    app.use(express.urlencoded());
    app.use(express.methodOverride());
    app.use(express.json());
    //app.use(express.bodyParser);
    app.use(app.router);
    app.use(express.static(path.join(__dirname, 'public')));
    app.use(logErrors);
    app.use(clientErrorHandler);
    app.use(errorHandler);
    //app.use(allowCrossDomain);

    // development only
    if ('development' == app.get('env')) {
      app.use(express.errorHandler());
    }

    //setup all the routes
    app.get('/', express.static(path.join(__dirname, 'public/index.html')));


    http.createServer(app).listen(app.get('port'),function(){
      console.log('Express server listening on port ' + app.get('port'));
    });

This is my app.js. Thanks in advance