How to externally pause and stop recursive javascript function

Question

I have a function which calls itself with a pause of 2 seconds until the ajax call returns 0. Now it can go on for a long time, hence i wish to pause it or stop it with an external event like a button click.

function create_abcd()
{
    var dataString = 'action=create_abcd&type=' + $('#abcd_type').val() + '&count=100';
    $.ajax({
        type: "POST",
        url: "backend.php",
        data: dataString,
        success: function(msg){
            if(msg != "0")
            {
                $("#abcd_output").append('<p>' + msg + '</p>')
                    setTimeout(create_abcd, 2000);
            }
            else
                return false;
        }
    });
}

any help would be greatly appreciated!

Have you made any attempt at solving this yourself? Should be as simple as setting a variable that is checked before the next iteration runs. — user1106925
– user1106925, Commented May 25, 2012 at 20:20
Yes, set a global variable with the button and have the function check the value of the variable on each run — hackartist
– hackartist, Commented May 25, 2012 at 20:21
that is something i did not think of! thanks. let me try that and come back here. sorry for being a noob, m new to js but i did try a lot before posting here. — Suyash
– Suyash, Commented May 25, 2012 at 20:23

Pierre · Accepted Answer · 2012-05-26 06:34:42Z

7

Something like:

var needStop = false;

function create_abcd()
{
    var dataString = 'action=create_abcd&type=' + $('#abcd_type').val() + '&count=100';
    $.ajax({
        type: "POST",
        url: "backend.php",
        data: dataString,
        success: function(msg){
            if(needStop) {
                needStop = false;
                return;
            }
            if(msg != "0")
            {
                $("#abcd_output").append('<p>' + msg + '</p>')
                    setTimeout(create_abcd, 2000);
            }
            else
                return false;
        }
    });
}

$('#button').click(function() {
    needStop = true;
});

=)

edited May 26, 2012 at 6:34

answered May 25, 2012 at 20:23

Pierre

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2 Comments

Suyash Over a year ago

Awesome!! you are a life saver. As for me, one dumb day at a time :)

Suyash Over a year ago

Update: The second solution worked perfectly but the first one would somehow keep going if i clicked pause during the execution of the function. It works when the function is not running.

Jakub Konecki · Accepted Answer · 2012-05-25 20:24:14Z

2

I think you're trying to solve your problem in a wrong way. You're obviously want to gen notified when some long-running process finishes on the server, so you poll every 2 secs. This will cause a lot of unnecessary requests.

Instead use push mechanism.

Consider using COMET, since you're PHP:

http://www.zeitoun.net/articles/comet_and_php/start

answered May 25, 2012 at 20:24

Jakub Konecki

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1 Comment

Suyash Over a year ago

actually no, the process is too huge to be executed in one go on a shared server as it will timeout. but thanks for this info! its a great read! something new to learn about, i can surely use it in my project!!

John Weldon · Accepted Answer · 2012-05-25 20:21:38Z

0

Create a global variable (or even a hidden input on the page).

Create a 'stop' button on the page.

When you click the 'stop' button you just set that input or variable to a special value.

At the top of your create_abcd just check that variable or input before proceeding. If the special value is set, just exit before setting the timeout again.

answered May 25, 2012 at 20:21

John Weldon

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1 Comment

Geert-Jan Over a year ago

to add to this: to be 100% sure the function isn't run again after the stop-button is clicked, you should capture the reference to the timeout function and call cleartimeout

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