jQuery recursive ajax poll using setTimeout to control the poll interval

Question

$(document).ready(function() {
    (function poll() {
        setTimeout(function() {
            $.ajax({
                url: "/project1/api/getAllUsers",
                type: "GET",
                success: function(data) {
                    console.log("polling");
                },
                dataType: "json",
                complete: poll,
                timeout: 5000
            }), 5000
        });
    })();
});

This just keeps executing as fast as the server can respond but I was hoping it would only poll every 5 seconds. Any suggestions?

EDIT: I should add, 5 seconds after the request has completed would be preferable.

It seems to be executing the next AJAX poll 5 seconds after the previous one has completed. What about that do you want to change? Best I can understand your question, that was what you wanted. — Richard Neil Ilagan, Jun 27 '12 at 10:13
@Richard Neil Ilagan: I want it to execute roughly every 5 seconds (5 seconds after the ajax request has completed is also fine and I'm told, better practice) but what I observe is that the request executes much more rapidly, as if it were ignoring the 5 second delay. — chrisjleu, Jun 27 '12 at 10:33
Sorry, just went out for dinner. Took a second look, and found where you seem to be getting it wrong. Popped up an answer below. — Richard Neil Ilagan, Jun 27 '12 at 11:41

score 7 · Accepted Answer · answered Jun 27 '12 at 11:41

It seems that you've managed to get your setTimeout delay argument written in the wrong place.

$(document).ready(function() {
  (function poll() {
    setTimeout(function() {
        $.ajax({
            url: "/project1/api/getAllUsers",
            type: "GET",
            success: function(data) {
                console.log("polling");
            },
            dataType: "json",
            complete: poll,
            timeout: 5000
        }) //, 5000  <-- oops.
    }, 5000); // <-- should be here instead
  })();
});

If you follow the braces, you'll see that you're calling setTimeout like:

setTimeout(function () {
    $.ajax(), 5000
})

and should be

setTimeout(function () {
    $.ajax();
}, 5000)

This should call the AJAX poll 5 seconds after the previous one has completed.

Nah, all good, I'd say. Happens to the best of us. Good luck with that. :) — Richard Neil Ilagan, Jun 27 '12 at 12:48

score 1 · Answer 2 · answered Jun 27 '12 at 10:16

If it should poll every 5 seconds and not necessarily 5 seconds after completing the last request, you could use setInterval. Don't know if that's acceptable, but it would make recursion unnecessary.

function poll() {

            $.ajax({
                url: "/project1/api/getAllUsers",
                type: "GET",
                success: function(data) {
                    console.log("polling");
                },
                dataType: "json"
        });
    }

setInterval(poll, 5000);

score 0 · Answer 3 · answered Feb 01 '18 at 13:42

Incase you wanted to use jQuery's promise syntax, rather than callback syntax here's another tidy way.

function poll() {
    $.get('http://your-api-endpoint.com')
    .done(function() {
        // 200 - OK response
    })
    .fail(function() {
        // Error Response
    })
    .always(function () {
        setTimeout(function() {
            poll();
        }, 5000);
    });
}

poll();

jQuery recursive ajax poll using setTimeout to control the poll interval

3 Answers3

Linked