How to send response using twice or more callback in one request

Question

I'm using express and the request POST look like that

router.post('/', function(req, res, next){
 var data = req.body;
 getRandom(data, function(value){
     res.json({value: value});
 });
});

POST is sent through ajax and then update textarea with new data.

 $.ajax({
           type: "POST",
           url: "/",
           data: JSON.stringify(datareq),
           dataType: 'json',
           contentType: 'application/json',
           success: function(x){
               $.each(x, function(index, value) {
                  $('.textarea').append(value + '\n');
               });
           },
           error: function(x) {
                console.log(x + 'error');
          }
       });

How to send this using one POST and a few response. User received one data in textarea when cb finished and then another data and so one till the end.

<textarea>
 data 1 - 1sec
 data 2 - 2sec leater
 data 3 - 3 second later
 ...
</textarea>

I add Time (1sec ...) only to show that callback has a lot to do to send another response.

Of course this not working because res.send() close connection and I received error

So how to achieve my idea, to sending simultaneously after post request. I want to give user data very fast, then another one when is ready not waiting for all and then send response.

score 5 · Accepted Answer · edited Dec 12 '19 at 09:16

You can't

Reason:

Http closes connection after sending response. You can not keep it open and sending multiple responses to the client. HTTP doesn't support it.

Solution 1:

Simply put a timer at client side and request periodically.

Solution 2 (Recommended):

Use socket, and pass data through it. socket.io is the socket library for nodejs applications. It is very easy to use. Set up a connection, keep sending data from server and receive it on client side.

Just to add on the answer. This answer explains why res.send closes the connection.

How to send response using twice or more callback in one request

1 Answers1