What is a quick and easy way to convert a Monero private key into a 24 word mnemonic seed?

Question

Is there a easy javascript way to convert a private key into a 24 word mnemonic seed? I understand that Monero private keys are generated using Base58, but where in code does it show me how to convert a private key to a mnemonic seed? I'm guessing I also need Monero's mnemonic seed dictionary list?

Answer 1

https://github.com/moneromooo-monero/monero-wallet-generator includes Javascript code to create a 25 word seed from a secret key. You can then chop off the last word to get a 24 word seed, since the last word is the checksum and is optional.

Specifically, you want the mn_encode function:

function mn_encode(str, wordset_name) {
    'use strict';
    wordset_name = wordset_name || mn_default_wordset;
    var wordset = mn_words[wordset_name];
    var out = [];
    var n = wordset.words.length;
    for (var j = 0; j < str.length; j += 8) {
        str = str.slice(0, j) + mn_swap_endian_4byte(str.slice(j, j + 8)) + str.slice(j + 8);
    }
    for (var i = 0; i < str.length; i += 8) {
        var x = parseInt(str.substr(i, 8), 16);
        var w1 = (x % n);
        var w2 = (Math.floor(x / n) + w1) % n;
        var w3 = (Math.floor(Math.floor(x / n) / n) + w2) % n;
        out = out.concat([wordset.words[w1], wordset.words[w2], wordset.words[w3]]);
    }
    if (wordset.prefix_len > 0) {
        out.push(out[mn_get_checksum_index(out, wordset.prefix_len)]);
    }
    return out.join(' ');
}

The words list and the helper functions it calls are in the same file.