How to send data from server to client via http?

I want to send the filepath of a file on my server to the client in order to play it using a media player. How can I retrieve that string on the client side in order to concatenate it in the src attribute of a <video element without using sockets?

Server snippet:

res.set('content-type', 'text/plain');
res.send('/files/download.mp4');

This is how you make a request to the server without any frameworks. "/path_to_page" is the route you set to the page that is supposed to process the request.

var xhr = new XMLHttpRequest();
xhr.open('GET', '/path_to_page', true);
xhr.onload = function(e) {
if (this.status == 200) {
  console.log(this.responseText); // output will be "/files/download.mp4"
}
};

xhr.send();
}

You might also want to send some params. 

var formdata = new FormData();
formdata.append("param_name", "value");

So you might for instance want to send the filename or such.

You just need to change 2 lines from the first code snippet. One would be 

 xhr.open('POST', '/path_to_page', true); // set to post to send the params

 xhr.send(formdata); // send the params

To get the params on the server, if you are using express, they are in req.body.param_name

Which framework are you using?? You can declare base path of your project directory in ajax and the followed by your file.

jQuery.ajax({
type: "GET",
url: "/files/download.mp4",

});

Since you are using express (on node), you could use socket.io:

Server:

var io = require('socket.io').listen(80),
    fs = require('fs');

io.sockets.on('connection', function (socket) {
   socket.on('download', function(req) {
      fs.readFile(req.path, function (err, data) {
         if (err) throw err;

         socket.emit('video', { video: data });
      });
   });
});

Client:

<script src="/socket.io/socket.io.js"></script>
<script>
  var socket = io.connect('http://localhost');

  ...      
  // request a download
  socket.emit('download', { path: '/files/download.mp4' });

  // receive a download
  socket.on('video', function (data) {
    // do sth with data.video;
  });
  ...
</script>

Edit: didnt notice you didnt want to use sockets. Still it is a viable solution.