What makes a simple substitution cipher algorithmically interesting?

What makes a simple substitution cipher algorithmically interesting?

That should have been a question for this PR: TheAlgorithms/Python#5251
I saw the algorithm is already in the site in Python and though about adding the JS version :)

I think this one is useful because someone studying ciphers might want to see the implementation in JavaScript.

What makes a simple substitution cipher algorithmically interesting?

That should have been a question for this PR: TheAlgorithms/Python#5251

True, but I'm afraid we are not the maintainers of the Python repo and we have different standards. We do not strive for parity with the other "algorithm" repos. In the future, please don't (mis)take other repos or legacy code in this repo as a good example for what to include.

I saw the algorithm is already in the site in Python and though about adding the JS version :)

I think this one is useful because someone studying ciphers might want to see the implementation in JavaScript.

Well, I find a good implementation pretty trivial and uninteresting, since it's just a substitution cipher (which also makes it an uninteresting cipher). For encoding, you just need a table from alphabet characters to code words, let's call it encoded. Then your encoding function is just plaintext => plaintext.replace(/[A-Z]/g, character => encoded[character]). Decoding is analogeously boring (since code words have fixed length): First flip the code table (const decoded = {}; for (const k in encoded) decoded[encoded[k]] = k, then chiffretext => chiffretext.replace(/[AB]{5}/, codeword => decoded[codeword]) is your decoding function.