Periodically send ajax requests

Question

There is a page and I want periodically to make "background" ajax requests. So the page is loaded then it should send ajax requests in a certain amount of time.

I might use cron for that. I have never use previously so I'm wondering if it would fit for that task. Is there any other more simple way?

P.S. The time delay will be about 5 minutes.

Richard Neil Ilagan · Accepted Answer · 2013-04-18T12:06:07.503

6

Since there is essentially an unknown delay between the time you send out an AJAX request and the time you receive a complete response for it, an oftentimes more elegant approach is to start the next AJAX call a fixed amount of time after the prior one finishes. This way, you can also ensure that your calls don't overlap.

var set_delay = 5000,
    callout = function () {
        $.ajax({
            /* blah */
        })
        .done(function (response) {
            // update the page
        })
        .always(function () {
            setTimeout(callout, set_delay);
        });
    };

// initial call
callout();

edited Apr 18 '13 at 12:06

answered Apr 17 '13 at 08:10

Richard Neil Ilagan

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where do I place the code for updating the part of a page? like `$('#my_id').text("the data is " + data.result);` – Alan Coromano Apr 18 '13 at 11:19
You can place that in a `.done()` callback against the AJAX, just as you would normally. – Richard Neil Ilagan Apr 18 '13 at 12:05
oo, man you are from Philippines. I'll be there in a couple of days! – Alan Coromano Apr 18 '13 at 12:08

Bitterzoet · Answer 2 · 2013-04-18T13:26:05.383

5

Cron is run on the serverside and you are using HTML and AJAX, so you should solve this issue in Javascript :-)

By using something like setInterval you can keep executing a function, your case might be something like polling a url via AJAX:

function updatePage(){
  // perform AJAX request
}
setInterval(updatePage, 5000);

edited Apr 18 '13 at 13:26

answered Apr 17 '13 at 08:05

Bitterzoet

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Elaborating @stecb's comment, do your best to never use the `eval` version of `setInterval()` ans `setTimeout()`. Always use a function directly, either by reference or by a direct lambda. – Richard Neil Ilagan Apr 18 '13 at 12:08
Right @RichardNeilIlagan :) I was with mobile.. ty ;) btw, it's also a matter of scope, passing it as a string will set a global scope for that foo. – stecb Apr 18 '13 at 13:34

score 1 · Answer 3 · edited May 23 '17 at 12:28

1

Depending on your rails version you may be able to use periodically_call_remote, otherwise you'll need the jquery alternative that @Bitterzoet described.

More info in this question.

edited May 23 '17 at 12:28

Community

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answered Apr 17 '13 at 08:09

Matt

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score 1 · Answer 4 · answered Apr 17 '13 at 08:23

You can send ajax request in four second like this:

setInterval(get_news, 4000);
        function get_news(){
             $.ajax('/dashboards/get_news', {
                type: 'POST',
                success: function(result) {
                    if(result > 0){
                        $('#div_1').text("See "+result+" new messages");
                        $('#div_1').show();
                    }
                    else{
                        $('#div_1').css('display', 'none');
                    }
                     },
                error: function() {
                    // alert("Error")
                }
            });       

        }

score 1 · Answer 5 · edited Apr 17 '13 at 08:49

Are you using jquery? If so, you can implement this method:

// first, you need asing a callback timer
var timeout = 300; //milliseconds

// this method contain your ajax request
function ajaxRequest() { //function to ajax request
    $.ajax({
        url: "/url/to/request/"
    }).done(function(data) {
        alert("response is: " + data);
    });
}


$(document).on("ready", function(){

    //this method will be called every 300 milliseconds
    setInterval(ajaxRequest, timeout);
});

Periodically send ajax requests

5 Answers5

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