The file md5.js provides md5(), a slight modification of Joseph Myers's high-performance function. Joseph's original functions have been wrapped in a self-invocating function so the only name added to the global namespace is md5(). In addition, the script will detect unicode and convert it to UTF-8 before hashing.
Due to the check for unicode and potential conversion to UTF-8, this function is slower that Joseph's original, but will produce identical results to server-side md5() functions executed on UTF-8-encoded text. There is a basic performance test at http://jsperf.com/md5-shootout.