Enable GZIP correctly

I am not able to enable GZIP on my website. It is hosted on nodejs server.

It shows gzip enabled when testing locally, but when deployed on the server I don't see response header in dev tools. Following is the code:

var compression = require('compression')
var express = require('express');
var app = express();
var server = require('http').createServer(app);

app.use(compression(9));
app.get('/', function(req, res){
  res.setHeader('Content-Encoding', 'gzip')
});

If I make following changes, I can see gzip enabled and response header coming from server as well, but many of my content fails to load with error like "http://127.0.0.1:3000/lib/jquery-ui.js net::ERR_CONTENT_DECODING_FAILED"

var compression = require('compression')
var express = require('express');
var app = express();
var server = require('http').createServer(app);

app.use(compression(9));
app.use(function(req, res, next) {
  res.setHeader('Content-Encoding', 'gzip, deflate');
return next();
});

via Abhinav Tyagi