Compess json data from rest of node.js use express compression

I created a small remainder of a node.js application. I am trying to compress json data that is returned by api request, but nothing is compressed. Use express and compression.

var express = require('express');
var methodOverride = require('method-override');
var bodyParser = require('body-parser');
var serveStatic = require('serve-static');
var compression = require('compression');

var app = express();
app.use(compression());

app.use(methodOverride('X-HTTP-Method-Override'));
app.use(bodyParser.json());
app.use(serveStatic('public', {'index': ['index.html']}));
app.use('/', require('./routes'));

app.use(function(req, res) {
    res.sendfile('public/index.html');
});

app.disable('x-powered-by');

var server = app.listen(3000, function () {
    var host = server.address().address;
    var port = server.address().port;
});

      

        
        
        
      

    

this response header without compilation = (((

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Content-Length: 3756
ETag: W/"56IqvwOVCBB3MRndvDsFTA=="
Vary: Accept-Encoding
Date: Wed, 10 Jun 2015 14:21:11 GMT
Connection: keep-alive

      

        
        
        
      

    

Reference.