Keep getting an error using bip39 npm package in nodejs?

Question

The error I get from below is: 'The "data" argument must be of type string or an instance of Buffer, TypedArray, or DataView. Received an instance of Promise'

When I console.log 'seed' I get Promise { }, but the tutorial for this has the code just like this.

Code:

const bip39 = require('bip39');
const hdkey = require('hdkey');

const mnemonic = bip39.generateMnemonic(); //generates a 12 word mnemonic

const seed = bip39.mnemonicToSeed(mnemonic); //creates seed buffer

const root = hdkey.fromMasterSeed(seed); //should not be passing a promise into here
//const masterPrivateKey = root.privateKey.toString('hex');

const addrnode = root.derive("m/44'/60'/0'/0/0");
console.log(seed);

Answer 1

Maybe your tutorial is out of date. In bip39's document, we have 2 kinds of mnemonicToSeed:

• mnemonicToSeed: Async function which returns Promise
• mnemonicToSeedSync: Sync function which returns Buffer

As your example, we have 2 ways to solve it following 2 above functions.

mnemonicToSeedSync

...
const seed = bip39.mnemonicToSeedSync(mnemonic); // creates seed buffer
...

mnemonicToSeed

(async () => { // wrap logic into a async function
  const mnemonic = bip39.generateMnemonic(); // generates a 12 word mnemonic

  // wait until seed finished to get seed Buffer
  const seed = await bip39.mnemonicToSeed(mnemonic); // creates seed buffer

  const root = hdkey.fromMasterSeed(seed); // should not be passing a promise into here
  //const masterPrivateKey = root.privateKey.toString('hex');

  const addrnode = root.derive("m/44'/60'/0'/0/0");
  console.log(seed);
})();