here is the code :
<div class="upload"><br>
<br>
<br>
<input type="hidden" value="" id="SWFUpload_0_3" name="jpg_uploaded_files[]">
<br>
<input type="hidden" value="" id="SWFUpload_0_4" name="jpg_uploaded_files[]">
<br>
<input type="hidden" value="" id="SWFUpload_0_5" name="jpg_uploaded_files[]">
<br>
<input type="hidden" value="" id="SWFUpload_0_6" name="jpg_uploaded_files[]">
<br>
<input type="hidden" value="" id="SWFUpload_0_7" name="jpg_uploaded_files[]">
<br>
<input type="hidden" value="" id="SWFUpload_0_8" name="jpg_uploaded_files[]">
<br>
</div>
Попробуйте использовать атрибут equals filter с type
атрибута
var len = $('.upload input[type="hidden"]').length
$("input[type='hidden']").length;