nodejs auto refresh view after database updates

Question

I would like use nodeJS to refresh my view, every time a function has made changes to the database. If we take MEAN-stack as an example, I don't want to send an $http-request every x seconds to check if changes have been made to the database. I would like the front end to get notified automatically and then update the view.

What are best practices for this? I would use some kind of Oberserver pattern in the server side, but do not know how I could notify the front end with that.

Solution

To get the front end to get notified automatically and then update the view you could use Socket.io framework. You can find all of the documentation on their site: http://socket.io/ And here is a basic example:

app.js ( to set up the server)

var http = require('http');
var express = require('express');
var port = normalizePort(process.env.PORT || '1000');
var app = express();
var server = http.createServer(app);
server.listen(port);

io = require('socket.io')(server);

///ROUTES
var routes = require('./routes/index')(io);
var users = require('./routes/users');
///////

I pass the io object to route index(and ofcourse there is a lot more stuff on app.js..this is just a basic example...).

mysql.js (to create a pool for connections)

var mysql = require("mysql");
var pool = mysql.createPool({
host     : 'host',
user     : 'user',
password : 'pass',
database : 'db_name',
connectionLimit: 1000
});

exports.pool = pool;

index.js

module.exports = function(io) {
 var express = require('express');
 var router = express.Router();
 var mysql = require('../mysql.js').pool;

 io.on('connection', function (socket) {
        socket.on('event_name', function (data) {
    mysql.getConnection(function(err,connection){
        if (err) {
          connection.release();
          return;
        }               
         connection.query("SQL STUFF",function(err,rows){
            if(rows.length>0){//checks if there are more than 0 rows returned.....
                socket.emit('do_something',data_you_want_to_pass);
            }
            else{
                socket.emit('do_something_else',data_you_want_to_pass);
            }
            connection.release();    
         });

          connection.on('error', function(err) {      
            return;    
          });
    });
  });

});

router.get('/', function(req, res) {
res.render("index"); 
});

return router;
}

And then on html page you have socket.emit and socket.on again.....

I recommend you take a look at the documentation and a few other examples...

I hope I helped you.