jQuery recursive ajax poll using setTimeout to control the poll interval - ajax

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.

Answer 1

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.

Answer 2

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);

Answer 3

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();