javascript setTimeout function out of scope

Question

I am trying to call showUpload(); from within two setTimeouts. Neither works. It seems to be out of scope and I'm not sure why. I tried this.showUpload() which didn't work either.

 $(document).ready(function(){
            var progress_key = $('#progress_key').val();

            // this sets up the progress bar
            $('#uploadform').submit(function() {
               setTimeout("showUpload()",1500);
               $("#progressbar").progressbar({ value:0}).fadeIn();
            });


            // uses ajax to poll the uploadprogress.php page with the id
            // deserializes the json string, and computes the percentage (integer)
            // update the jQuery progress bar
            // sets a timer for the next poll in 750ms
            function showUpload() {
                $.get("/myid/videos/uploadprogress/" + progress_key, function(data) {
                    if (!data)
                        return;

                    var response;
                    eval ("response = " + data);

                    if (!response)
                        return;

                    var percentage = Math.floor(100 * parseInt(response['bytes_uploaded']) / parseInt(response['bytes_total']));
                    $("#progressbar").progressbar({ value:percentage})

                });
                setTimeout("showUpload()", 750);
            }
        });

Thank you for your time.

pkaeding · Accepted Answer · 2010-05-28 00:47:03Z

2

As @Daniel said, this should work:

setTimeout(showUpload, 750);

Please note that the quotes should be removed (this is why it isn't being executed until the timeout runs out). Right now, you are passing a string, which is evaled when the timeout runs out. This eval will happen in a different scope, which is why you are seeing the problem you are seeing.

Instead, passing a reference to the showUpload function to setTimeout will allow your function to be executed later. Keep in mind that when it runs, it will be in a different scope, so you may have other scope issues, like with progress_key. You will need to create a closure around showUpload to capture that parameter.

answered May 28, 2010 at 0:47

pkaeding

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Comments

Daniel Vassallo · Accepted Answer · 2010-05-28 00:36:38Z

2

It looks like you need to remove the parenthesis from showUpload in both your setTimeout calls. Otherwise you will be invoking the showUpload method instead of passing it as a parameter:

setTimeout(showUpload, 750);

answered May 28, 2010 at 0:36

Daniel Vassallo

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2 Comments

Nick Craver Over a year ago

The intent is right, though the description is a bit off, you're calling the method with the parenthesis, but you're trying to invoke a method in the global space when it's a string...where it doesn't exist, the direct reference like you have is the correct approach.

Daniel Vassallo Over a year ago

@Nick: Thanks for the note... I was just looking for some references on how setTimeout() evals code when passed as a string.

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