Выдача рандомного кода с сервера

const express = require('express');
const app = express();
const str_rand = () => {
    let result = '';
    const words = '0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM'; 
    while(result.length < 15) result += words[Math.floor(Math.random()*words.length)];
    return result;
}
app.use('/code', (req, res) => res.end(str_rand()));
app.use('/', (req, res) => res.end(`
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
    <li>
      <label for="first-name">Your code:</label>
      <input type="text" name="code" id="short_link" style="border: 1px solid #3E7EFF; border-radius: 5px 5px 5px 5px;" value="${str_rand()}">
    </li>
    <li>
      <div id="gen" style="cursor: pointer" ;>Generate</div>
    </li>   
    <script>    
        $("#gen").click(() => $.get('/code', code => $("#short_link").val(code)));
    </script>
`));
app.listen(8888, () => console.log('Started http://localhost:8888'));

router.get('/', checkAuthentication, function(req, res){
    ////тут генерить инфу и слать 
    res.json({"some inf"});
});