Parse format of value from client to server in nodeJS

Question

I have a nodeJS app

I'm trying to send the user-agent value that I got from the client side using navigator.userAgent to the server side using ajax.

PS : I know I can access the user-agent from the server. I am aware of that. I am doing this for a certain purpose.

As follows :

window.addEventListener('DOMContentLoaded', async() => {
            $.ajax({
            type:'POST',
            url:'/UA/send/',
                    data: navigator.userAgent })             
});

In my nodeJS server, I am reading it like that:

app.post('/UA/send', function(req, res) 
{  
        console.log(req.body));
});

This returns

{ 'Mozilla/5.0 (X11; Linux x86_64) Chrome/64.0.3282.140 Safari/537.36': '' }

I added alert(navigator.userAgent); to my javascript code and I got this :

Mozilla/5.0 (X11; Linux x86_64) Chrome/64.0.3282.140 Safari/537.36

Why am I getting it in the following format to the server side? And how could I parse and read it?

Answer 1

When posting a JSON using $.ajax , you have to use JSON.stringify , and 'Content-Type': 'application/json' header, otherwise you're sending form data. In your example you were sending the user agent as key, and no value.

That's why the posted object looked like: { [userAgentValue]: ''}

Use this for posting a JSON.

 $.ajax({
      type:'POST',
      url:'/UA/send/',
      headers: { 'Content-Type': 'application/json' },
      data: JSON.stringify({ userAgent: navigator.userAgent })
 });

With the correct body parser on your server:

app.use(bodyParser.json());

Now you will receive:

{ userAgent: 'Mozilla/5.0 (X11; Linux x86_64) Chrome/64.0.3282.140 Safari/537.36' }

---

If you're not trying to post a JSON, and you're using: application/x-www-form-urlencoded

$.ajax({
     type:'POST',
     url:'/UA/send/',
     data: { userAgent: navigator.userAgent }
 });

And on your server:

app.use(bodyParser.urlencoded({ extended: false }));