How to get value of URL parameter in Node.js?

Question

For example I have this URL: http://localhost/chat.html?channel=talk How can I get the value of parameter channel in Node.js? I want to store the value of channel in a variable.

I changed server.get to this:

server.get("/channel", (req, res) => {
    let query = url.parse(req.url, true).query;
    console.log(req.query.channel);
    let rueckgabe = {
        channel: req.query.channel
    };
    res.send(JSON.stringify(rueckgabe));
});

Now I'm expecting an output of the value of channel on my console but nothing appears.

This is the full code of index.js:

//Server erstellen
const express = require("express");
let server = express();
server.use(express.static("public"));

//Socket.io
const http = require("http");
let httpServer = http.Server(server);
const socketIo = require("socket.io");
let io = socketIo(httpServer);

//Eventlistener bei Verbindungsaufbau
io.on("connection", (socket) => {
    console.log(socket.id);

    socket.on("chatnachricht", eingabe => {
        io.emit("nachricht", eingabe);
    });
});

let stdIn = process.openStdin();
stdIn.addListener("data", (eingabe) => {
    io.emit("nachricht", eingabe.toString());
});

server.get("/channel", (req, res) => {
    let query = url.parse(req.url, true).query;
    console.log(query);
    let rueckgabe = {
        channel: query.channel
    };
    //res.send(JSON.stringify(rueckgabe));
    res.send(JSON.stringify(rueckgabe));
});

httpServer.listen(80, () => {
    console.log("Server läuft");
});

SOLUTION

This code works so far but with limitations:

//Server erstellen
const express = require("express");
let server = express();
server.use(express.static("public"));

const http = require("http");
let httpServer = http.Server(server);
const socketIo = require("socket.io");
let io = socketIo(httpServer);
var router = express.Router();
const url = require("url");
var path = require('path');


//Eventlistener bei Verbindungsaufbau
io.on("connection", (socket) => {
    console.log(socket.id);

    socket.on("chatnachricht", eingabe => {
        io.emit("nachricht", eingabe);
    });
});

/*
let stdIn = process.openStdin();
stdIn.addListener("data", (eingabe) => {
    io.emit("nachricht", eingabe.toString());
});
*/

server.get("/chat", (req, res) => {
    let query = url.parse(req.url, true).query;
    console.log(query.channel);
    let rueckgabe = {
        channel: query.channel
    };
    res.sendFile('chat.html', { root: path.join(__dirname, 'public/') });
    //res.send(JSON.stringify(rueckgabe));
});

httpServer.listen(80, () => {
    console.log("Server läuft");
});

Now it works with server.get() but I can't use both res.sendFile('chat.html', { root: path.join(__dirname, 'public/') }); and res.send(JSON.stringify(rueckgabe));. How can I use both?

Answer 1

It looks like you're using the Express framework for Node.

From the docs, query string params may be accessed via req.query:

server.get("/channel", (req, res) => {
    let id = req.query.id; // where "id" is a paramter on the query string
}

And if you need the full URL of the request:

server.get("/channel", (req, res) => {
    let fullUrl = req.protocol + '://' + req.get('host') + req.originalUrl;
}

Answer 2

Well you mentioned for this url http://localhost/chat.html?channel=talk you're not seeing the channel parameter in the server. That's because you aren't hitting the endpoint that you've defined.

Copy of your code from above

server.get("/channel", (req, res) => {
    let query = url.parse(req.url, true).query;
    console.log(req.query.channel);
    let rueckgabe = {
        channel: req.query.channel
    };
    res.send(JSON.stringify(rueckgabe));
});

You're setting the /channel url here. With this configuration if you want to get the query parameter you need to call http://localhost:{portnumber}/channel?channel=somerandomvalue

If you want to have the /chat url change your configuration like this:

server.get("/chat", (req, res) => {
    let query = url.parse(req.url, true).query;
    console.log(req.query.channel);
    let rueckgabe = {
        channel: req.query.channel
    };
    res.send(JSON.stringify(rueckgabe));
});

and call into http://localhost:{portnumber}/chat?channel=somerandomvalue

If you want to serve a static html while using the url name as the same file name you can do something like this:

var router = express.Router();
var path = require('path');

router.get('/chat', function(req, res) {
    // where chat.html is in the public directory
    console.log(req.query.channel);
    res.sendFile('chat.html', { root: path.join(__dirname, '../public/') });
});