How to generate md5 files on the client side before sending to avoid repeating files?

Question

JavaScript

The point of the code is to check if the server has the file that the user wants to upload. So that it does not wait a long time for the file to be uploaded, and then breaks off, it will naturally be more prudent to first check whether such a file already exists, and then upload it if it does not exist. Naturally, the md5 of the file will be verified, and not the file itself.

How to generate md5 file on client side before sending it? How to do it in Javascript? Or in what other languages ​​can this be done on the client side?

Answer 1

Note that trusting data submitted by a user is very dangerous
How to read the file
www.html5rocks.com/en/tutorials/file/dndfiles Hashing
Libraries
stackoverflow.com/questions/1655769/fastest-md5-im...
Start at
https:// code.google.com/p/crypto-js/
https://github.com/blueimp/JavaScript-MD5
pajhome.org.uk/crypt/md5 Hash
creation rate
jsperf.com/md5-shootout/63