Make polling to a webservice with jQuery

Question

I need to poll a webservice once an hour to check for new messages. I want to do it with jQuery. The ajax call would be like this:

function checkForMessages(rowid) {
$.ajax({
    type: "POST",
    url: "MyPage.aspx/CheckForMessages",
    contentType: "application/json; charset=utf-8",
    data: "{'currentMessages': '" + cMessages+ "'}",
    dataType: "json",
    success: function (msg) {

    },
    error: function (response) {

    }
});
}

url: "MyPage.aspx/CheckForMessages" is actually a PageMethod instead of Webservice.

What I don't understand is how to make the "loop" with jquery that waits an hour to call the above function.

So how can I make the code that calls this function only once an hour?

You're expecting someone to keep the site open and not timeout for more than 1 hour? — Rory McCrossan, Jan 14 '13 at 15:21
@RoryMcCrossan, dunno. Maybe it's for a dashboard or something. — Jonathan M, Jan 14 '13 at 15:32

score 0 · Answer 1 · edited Nov 17 '14 at 10:04

0

window.setIntervall(function, delay);

delay in miliseconds.

However, with this method the site must always be open. You could use Server Sent Events to push a message from the server to your site, but this requires a lot of work..

edited Nov 17 '14 at 10:04

Yohanes Khosiawan 许先汉

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answered Jan 14 '13 at 15:24

mercsen

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I prefer polling than pushing at the moment. – anmarti Jan 14 '13 at 15:43

Reinstate Monica Cellio · Answer 2 · 2013-01-14T15:37:31.710

0

Look at setInterval()...

http://www.w3schools.com/jsref/met_win_setinterval.asp

setInterval(checkForMessages, 3600000);

edited Jan 14 '13 at 15:37

answered Jan 14 '13 at 15:25

Reinstate Monica Cellio

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score 0 · Answer 3 · answered Jan 14 '13 at 15:25

window.setInterval is the best method for this, obviously it will only poll after an hour if the webpage is still open.

$(function () {
    setInterval(myPollingMethod, 3600000);
});

function myPollingMethod()
{
  //this will repeat every 1 hour (3600 seconds)
}

Also don't forget to call the window.clearInterval method if you want to stop polling.

Jonathan M · Answer 4 · 2013-01-14T15:46:42.023

0

function checkForMessages(rowid) {
$.ajax({
    type: "POST",
    url: "MyPage.aspx/CheckForMessages",
    contentType: "application/json; charset=utf-8",
    data: "{'currentMessages': '" + cMessages+ "'}",
    dataType: "json",
    success: function (msg) {
        //do stuff here
        setTimeout(function(rowid) {checkForMessages(rowid);},3600000);
    },
    error: function (response) {

    }
});
}

edited Jan 14 '13 at 15:46

answered Jan 14 '13 at 15:26

Jonathan M

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That will run the function `checkForMessages` immediately. – Reinstate Monica Cellio Jan 14 '13 at 15:36

tpeczek · Accepted Answer · 2013-01-14T15:42:20.927

0

You can use setTimeout function in order to achieve the desired result:

function checkForMessages(rowid) {
    $.ajax({
        type: "POST",
        url: "MyPage.aspx/CheckForMessages",
        contentType: "application/json; charset=utf-8",
        data: "{'currentMessages': '" + cMessages+ "'}",
        dataType: "json",
        success: function (msg) {
            ...
        },
        error: function (response) {
            ...
        },
        complete: function() {
            ...
            setTimeout(function() { checkForMessages(rowid); }, 3600000);
        }
    });
}

This way when you call your function for first time and your $.ajax call is finished (regardless if it was success or error) it will schedule to execute the function again after one hour (but please remember that one hour is a lot of time in web world, authorization might expire etc.).

edited Jan 14 '13 at 15:42

answered Jan 14 '13 at 15:29

tpeczek

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what is the advantage of using setTimeout, and then adding it again once it has elapsed over using setInterval? The latter is cleaner IMO – Steve Jan 14 '13 at 15:39
@Steve The differences are very subtle, you can read more about them here: http://stackoverflow.com/questions/729921/settimeout-or-setinterval. In this case they are not relevant but setTimeout is always more reliable to me and because of that it is always my first choice. – tpeczek Jan 14 '13 at 15:48
@Archer Fixed the parameter passing. – tpeczek Jan 14 '13 at 15:50
@a_maar This is why there is a `setTimeout` call in `complete` callback - this one is called regardless if $.ajax fail or success. – tpeczek Jan 16 '13 at 14:00
My `complete` callback is not triggered. Do I have to include both the `success` and `error` as well as `complete` ? – anmarti Jan 16 '13 at 14:02
It seems `complete` must go with at least `success`. So I needed to deal with both `complete` and `success`. `complete` to do the *loop* and `success` to do the *stuff* – anmarti Jan 16 '13 at 14:12

Make polling to a webservice with jQuery

5 Answers5