I am trying to understand how to generate addresses from 1 mnemonic for multiple cryptocurrencies.

I needed a read-only wallet, so I guess I need to use an xpub key. But I am struggling to understand wallet tree structure and how to accomplish it.

Till now I am able to do this.

const bip39 = require('bip39')
var HDKey = require('hdkey')


const mnemonic = bip39.generateMnemonic()
const seed = bip39.mnemonicToSeedSync(mnemonic).toString('hex')
let hdkey = HDKey.fromMasterSeed(Buffer.from(seed, 'hex'))
var childkey = hdkey.derive("m/0/0/1")
console.log(childkey.publicExtendedKey);

let publicExtendedKey = hdkey.publicExtendedKey;
hdkey.publicKey

My requirement is a user can save 1 mnemonic on his side, and I have a public key using which I can generate addresses for multiple cr