How to GET id or any variable data from Query String in Node Js Server?

Question

I have Setup a Node Js Server. Right now I am fetching records of all users from Database.

Now if I want a specific User of a specific Id , how can I pass it to Node Js ?

For Example : We do in PHP : $_GET['id']; I want the same thing in Node JS.

Here is my Server Code :

var app                 = require('http').createServer(),
    io                  = require('socket.io').listen(app),
    fs                  = require('fs'),
    mysql               = require('mysql'),
    connectionsArray    = [],
    connection          = mysql.createConnection({
        host        : 'localhost',
        user        : 'root',
        password    : '',
        database    : 'test',
        port        : 3306
    }),
    POLLING_INTERVAL = 1000,
    pollingTimer;

// If there is an error connecting to the database
connection.connect(function(err) {
  // connected! (unless `err` is set)
  console.log( err );
});

// creating the server ( localhost:8000 )
app.listen(8000);


/*
*
* HERE IT IS THE COOL PART
* This function loops on itself since there are sockets connected to the page
* sending the result of the database query after a constant interval
*
*/

var pollingLoop = function () {

    // Doing the database query
    var query = connection.query('SELECT * FROM users'),
        users = []; // this array will contain the result of our db query

    // setting the query listeners
    query
    .on('error', function(err) {
        // Handle error, and 'end' event will be emitted after this as well
        console.log( err );
        updateSockets( err );
    })
    .on('result', function( user ) {
        // it fills our array looping on each user row inside the db
        users.push( user );
    })
    .on('end',function(){
        // loop on itself only if there are sockets still connected
        if(connectionsArray.length) {
            pollingTimer = setTimeout( pollingLoop, POLLING_INTERVAL );

            updateSockets({users:users});
        }
    });

};


// creating a new websocket to keep the content updated without any AJAX request
io.sockets.on( 'connection', function ( socket ) {

    console.log('Number of connections:' + connectionsArray.length);
    // starting the loop only if at least there is one user connected
    if (!connectionsArray.length) {
        pollingLoop();
    }

    socket.on('disconnect', function () {
        var socketIndex = connectionsArray.indexOf( socket );
        console.log('socket = ' + socketIndex + ' disconnected');
        if (socketIndex >= 0) {
            connectionsArray.splice( socketIndex, 1 );
        }
    });
    socket.on('ddd', function (name) {
        socket.username=name;
    });


    console.log( 'A new socket is connected!' );
    connectionsArray.push( socket );

});

var updateSockets = function ( data ) {
    // adding the time of the last update
    data.time = new Date();
    // sending new data to all the sockets connected
    connectionsArray.forEach(function( tmpSocket ){
        tmpSocket.volatile.emit( 'notification' , data );
    });
};

You don't have to reinvent the wheel here. You can use express server which parses the body and gives the query string your you. — user568109
– user568109, Commented Nov 5, 2013 at 9:16
WebSockets don't have GET or POST variables. To send a parameter with socket.io, you have to .emit() an event with it in the data Object. — Jonathan Lonowski
– Jonathan Lonowski, Commented Nov 5, 2013 at 9:23

Community · Accepted Answer · 2017-05-23 11:50:06Z

1

First you have to embed the socket.io JavaScript for client side:

script(rel="text/javascript" src="/js/libraries/socket.io.min.js");

Then you connect to your socket server like this:

var socket = io.connect("https://localhost:8080");

After you connected, you can fire off events:

button.on("click", function(){
    socket.emit("event-name", { userId : 2 });
});

On server side you have the corresponding listener:

socket.on("event-name", function(data){
    console.log(data.userId); // logs: 2

    var query = // ...

    socket.emit("response", query);
});

On client side yet again, you retrieve the response:

socket.on("response", function(data){
    console.log(data); // logs: the query
});

To determine which client should receive an emit please see:

socket.io rooms or namespacing?

For authorizing please see:

https://github.com/LearnBoost/socket.io/wiki/Authorizing

edited May 23, 2017 at 11:50

CommunityBot

11 silver badge

answered Nov 5, 2013 at 12:03

Matthias Holdorf

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