Strength and weaknesses of this JavaScript charCodeAt based login script
You don't need to brute force it. Since the passcode is the product of all its character codes, you can just find all prime factors of the passcode. I used an online tool which yields $2^6\cdot 3\cdot 5\cdot 7^2\cdot 61^2\cdot 97$. It looks like an ASCII passcode of length 5.

This doesn't get you anywhere since this is just a check for a web page to open. Now you need to "brute force" all possible combinations of $2^6\cdot 3\cdot 5\cdot 7^2\cdot 61^2$ ($97$ is more of less fixed to be a) and then try for each combination all permutations. You can further filter a little since only lowercase letters are used. For each permutation you would need to download the password+'.html' file. When you finally get an HTTP 200 code you're done.

Of course if you assume that every letter is lowercase then you can assume that $2\cdot 61$ is z. Now the question is to find a 5 letter word with letter zza in it.... The other prime factors will get you p and i.

Note that you only need to do this for passcode, usercode is not used.