Chrome file upload bug: on change event won't

问题:

I am working on this html5 file uploader plugin but it has a bug on Google Chrome which I can't understand and fix it. It works fine on Firefox.

jsfiddle link

The problem is that you cannot upload the same file twice from your desktop.

When you first click, select, and hit OK to upload a file from your desktop, it should alert a message, for instance '.button-1' - depends on which upload button you click.

Then if you try to upload the same file again, this line of code won't be executed anymore,

$(".upload-file",object_parent).change(function() {

             ...
             ...

             alert($cm.selector);

});

Any idea what goes wrong in this plugin?

(function($){

    // Attach this new method to jQuery
    $.fn.extend({ 

        // This is where you write your plugin's name
        upload_file_html5: function(options) {

            // Set the default values, use comma to separate the settings, example:
            var defaults = {
                objectSuperparent:    '.media'
            }

            var options =  $.extend(defaults, options);
            var o = options;

            var $cm = this.click(function(e){

                // <a> button is the object in this case.
                var object = $(this);

                // Get other info from the element belong to this object group.
                var object_href = object.attr('href');
                var object_parent = object.parent();
                alert($cm.selector);

                // Trigger the click event on the element.
                // Due to security policies triggering click on the input type=file is not allowed/supported in some browsers and Opera is one of them.
                //$('input[type=file]').trigger('click'); // or:
                $(".upload-file",object_parent).click();

                return false;

            });

            // Trigger ajax post when ever the file is changed by the user.
            var $cm_2 = $(".upload-file").change(function(){

                // <input> is the object in this case.
                var object = $(this);

                var object_form = object.parent();
                var object_superparent = object.parents(o.objectSuperparent);
                var path_config = $($cm.selector,object_superparent).attr('href');
                var path_post = object_form.attr('action');

                alert($cm.selector);
                //alert(path_config);

                ....
                ....

            });

        }
    });

})(jQuery);

It was working OK on Chrome but just failed recently, probably Chrome has updated a latest version to my machine and this update causes the bug?

回答1:

Yes. My Chrome has different behavior to Firefox, but I think Chrome is correct.

According to W3C's document:

onchange event occurs when a control loses the input focus and its value has been modified since gaining focus

if you try to upload the same file, the value of file input does not change. Try to print it out:

$('.button-2').click(function(){
    console.log($(".list .upload-file").val())
    return false;
});

回答2:

If you want to upload twice, clear file input value

$('input[type="file"]').val(null);

jsfiddle test

回答3:

it might be that the input is being re-rendered. For whatever reason this may be, for me its irrelevant. The $.on('change', callback) functionality is lost.

Try using .delegate function which I absolutely love! http://api.jquery.com/delegate/

Ok so delegate is exactly the same, it just tells jquery if there is an element rendered on screen with a particular handle, attach a functionality to it.

So even if the element is re-rendered, it will still keep to function.

$(document).delegate('.file_upload_btn', 'change', function(){});

You may think this is a throw away function & say whats the difference but this has saved me a lot of time on projects.