Easiest way to do is what @Molo mentioned in his comment.
$('#element_id').trigger("click"); OR $('.element_class').trigger("click");
$('#element_id').trigger("mousedown"); OR $('.element_class').trigger("mousedown");
Or you could, reset the .html() of the upload element
$('#'+id).html($('#'+id).html()); OR $('.'+class).html($('.'+class).html());