Lightest way to set a client screen size validation in node.js before sending web app files?

I code a web app with node.js and socket.io. I dont want clients with a device screen smaller than 500px*500px to load the game. I want to verify client screen size server side, then send heavy game files or just a little html caution if the device screen isn't large enough. I try to avoid cookies. Is this possible?

Thanks

Solution

in the server:

socket.emit('screen');
socket.on('size', data => {
   let width = data.width,
       height = data.height;         
   //some code here
});

in the client (using jQuery):

socket.on('screen', () => {
    let width = $(window).width(),   
        height = $(window).height(); 
    socket.emit('size', {width, height});
});

If you don't use jQuery you can send window.innerWidth and window.innerHeight respectively.

You can do easily it at the client side. Have a look at the simple example:

server.js

const express = require('express');
const app = express();

app.get('/', (req,res) => {
    res.sendFile(__dirname + '/hello.html');
});
app.get('/small', (req,res) => {
    res.sendFile(__dirname + '/small.html');
});
app.get('/game', (req,res) => {
    res.sendFile(__dirname + '/game.html');
});

app.listen(3000);

hello.html

<html>
<body>
    <h1>Hello</h1>
    <script>
        if (window.innerWidth < 500 || window.innerHeight < 500) {
            window.location.assign('small');
        } else {
            window.location.assign('game');
        }
    </script>
</body>
</html>

small.html

<html>
<body>
    <h1>Small screen :-(</h1>
</body>
</html>

game.html

<html>
<body>
    <h1>Loading The Game</h1>
</body>
</html>