setTimeout直到我停止页面才开始

Question

On the event of a form submit, I have a jquery ajax function that queries for the amount of data uploaded from a file that I can use in making a progress bar. This is my js file:

var submitted = '';
var counter = 0;

$('#webfileuploadform').submit(function(){

    if(submitted == 'submitted') return false; // prevents multiple submits

    var freq = 1000; // freqency of update in ms
    var progress_url = '/upload_progress/' + $('#id_progress_id').val(); // ajax view serving progress info

    update_progress_bar();

    function update_progress_bar(){
        $.ajax({
            dataType:"json",
            url: progress_url,
            success: function(data){
                    counter ++
                console.log('hit success ' + counter);
            },
            complete: function(jqXHR, status){
                if (status == 'success'){
                    console.log('hit complete', status == success')
                } else {
                    console.lot('hit complete', status == something else')
                }
            }
        });
        setTimeout(function(){update_progress_bar()}, freq);
    }

    submitted = 'submitted'; // marks form as submitted

});

So, the user will use the form to select the file then click submit. This all happens just fine. The form submits, the file is uploaded, and the progress shows just fine when I open my ajax view in a separate tab and keep refreshing it. What I don't understand is why the update_progress_bar function runs once until I stop the page. I'll upload a file but until I click the 'x' on my browser I won't get any of the 'hit success' in my console. After I hit stop, the console spits out the 'hit success ' plus the counter. But I shouldn't have to hit stop to do this. I need this to work when the file is uploading.

Any ideas what my problem is?

**

EDIT

**

Not sure if it makes a difference, but I am doing all this on a django development server. Which I think shouldn't have a problem with two XMLHTTPRequests in the same session.

Answer 1

Try this:

var $submitted = '';

$('#webfileuploadform').submit(function(){

    if($submitted == 'submitted') return false; // prevents multiple submits

    var freq = 1000; // freqency of update in ms

    update_progress_bar();

    function update_progress_bar(){
        var progress_url = '/upload_progress/' + $('#id_progress_id').val(); // ajax view serving progress info

        $.ajax({
            dataType:"json",
            url: progress_url,
            success: function(data){
                console.log("hit success");
            },
            complete:function(jqXHR, status) {
                if (status == 'success') {
                    setTimeout(update_progress_bar, freq);
                }
            }
        });
    }

    $submitted = 'submitted'; // marks form as submitted

});

Answer 2

As it stands, the code looks good to me. I would add some more console logging to make sure the ajax call is returning with the status you expect:

complete:function(jqXHR, status) {
    console.log('got to complete, status: ', status);
    if (status == 'success') {
         console.log('status is success, calling setTimeout.');
         setTimeout(update_progress_bar, freq);
    }
}

Answer 3

In the ajax function I set the async setting to false:

$.ajax({
    async: false,
    ...
});

This has solved the problem. I have no idea how. From what I understand, this setting forces the ajax request to wait until all other http requests are finished before allowing it to continue. With that being the case, I have no idea how this works. I'll keep from answering my own question in case someone knows why this is working this way...