I'm currently using this as a way to check if Monero addresses are valid in my application. However, it does not check sub-addresses and I'm trying to filter integrated addresses out.
I can't find any info on the web to check if a Monero subaddress is valid and it would be nice if I didn't have to use RPC.
You do not need to use the RPC to do things such as validating an address. See the source code for https://xmr.llcoins.net/addresstests.html, as that shows how you can decode an address using just javascript.
Also see https://monerodocs.org/public-address/standard-address/ and https://monerodocs.org/public-address/subaddress/.
Standard addresses and subaddresses have the exact same format, with the difference between them being the value of the "network byte".
For mainnet, and you don't mind being a bit hacky, you can run the code you point to. If it doesn't like the address, then check if it starts with '8'. If yes, replace 8 with 4 and try again. If it likes it, it was a subaddress.
