jQuery Load Progress Bar

I'm sure this question HAS to have been asked, but after searching through the 'Related Questions' here as well as several Google searches... I have come up empty.

I'm simply trying to implement a true bytes_loaded/bytes_total type of progress bar in jQuery or even traditional Js. This was so easy in the AS3 days :) ...but of course Flash comes with it's drawbacks. All I really need to know is how to calculate the current bytes loaded and bytes total during any download. Calculating the uploaded bytes woul开发者_StackOverflow社区d be sweet too. Anyone have another posted question to direct me to? Or have knowledge of the subject?

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There is a Q/A on progress bars for long process reporting on the server. Also check out how to get AJAX download progress in every browser but IE.

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There are frameworks/plugins for this available:
http://blog.stevensanderson.com/2008/11/24/jquery-ajax-uploader-plugin-with-progress-bar/
http://webdeveloperplus.com/jquery/multiple-file-upload-with-progress-bar-using-jquery/
and so on...