UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'fromSeedBuffer' of undefined I am getting Getting error at this line
var root = bitcoin.HDNode.fromSeedBuffer(seed);


  UnhandledPromiseRejectionWarning: TypeError: Cannot read property
  'fromSeedBuffer' of undefined


Here is the code snippet to generate bitcoin address:

'use strict'

var bip39 = require('bip39');
var bitcoin = require('bitcoinjs-lib');

var mnemonic = bip39.generateMnemonic();
if (bip39.validateMnemonic(mnemonic)) {
    console.log('\nThe mnemonic is \n' + mnemonic);
    var seed = bip39.mnemonicToSeed(mnemonic);
    var root = bitcoin.HDNode.fromSeedBuffer(seed);
    var dp = root.derivePath("m/140'/0'/0'/0/5");

    console.log('\nThe Address is \n' + dp.getAddress());    
} else {

}


Where bitcoinjs-lib v4.0.0 and 
      bip39 v2.5.0 and node v8.0
Try using the bip32 module. Also there are a few other things you'll need to fix as well. See Use BIP39 to generate BIP32 addresses. Note, this will generate a P2PKH address, see getAddress() function.

index.js:

'use strict'

var bip39 = require('bip39');
var bip32 = require('bip32');
var bitcoin = require('bitcoinjs-lib');

function getAddress (node, network) {
  return bitcoin.payments.p2pkh({ pubkey: node.publicKey, network }).address
}

var mnemonic = bip39.generateMnemonic();
if (bip39.validateMnemonic(mnemonic)) {
    console.log('\nThe mnemonic is \n' + mnemonic);
    var seed = bip39.mnemonicToSeed(mnemonic);
    var root = bip32.fromSeed(seed);
    var dp = root.derivePath("m/140'/0'/0'/0/5");

    console.log('\nThe Address is \n' + getAddress(dp));    
} else {

}


Output:

$ node index.js

The mnemonic is
assume victory kiwi swarm furnace firm thumb exact dizzy crucial neglect certain

The Address is
1FYtPnUZZ2ZJL2fZ6XehGtkHfujUHkqK3T