main.js

// Add imports here
const BIP39 = require("bip39");
const hdkey = require("ethereumjs-wallet/hdkey");
const Wallet = require("ethereumjs-wallet");
const keccak256 = require("js-sha3").keccak256;
const EthereumTx = require("ethereumjs-tx");



// Add functions here
// Generate a random mnemonic (uses crypto.randomBytes under the hood), defaults to 128-bits of entropy
function generateMnemonic(){
    return BIP39.generateMnemonic();
}

//validate if a string of characters is a valid mnemonics 
var isValid = BIP39.validateMnemonic("Enter your mnemonic here"); 
// this will return false because "Enter your mnemonic here" is not a valid phrase

function generateSeed(mnemonic){
    return BIP39.mnemonicToSeed(mnemonic);
}

function generatePrivKey(mnemonic){
    const seed = generateSeed(mnemonic);
    return hdkey.fromMasterSeed(seed).derivePath(`m/44' /60' /0' /0/0`).getWallet().getPrivateKey();
}

function derivePubKey(privKey){
    const wallet = Wallet.fromPrivateKey(privKey);
    return wallet.getPublicKey();
}

function deriveEthAddress(pubKey){
    const address = keccak256(pubKey);//keccak256 hash of publicKey
    //Get the last 20 bytes of the public key 
    return "0x" + address.substring(address.length - 40, address.length);
}

function signTx(privKey, txData){
    const tx = new EthereumTx(txData);
    tx.sign(privKey);
    return tx;
}

function getSignerAddress(signedTx){
    return "0x" + signedTx.getSenderAddress().toString('hex');
}


/*

Do not edit code below this line.

*/

var mnemonicVue = new Vue({
    el:"#app",
    data: {  
        mnemonic: "",
        privKey: "",
        pubKey: "",
        ETHaddress: "",
        sampleTransaction: {
            nonce: '0x00',
            gasPrice: '0x09184e72a000', 
            gasLimit: '0x2710',
            to: '0x31c1c0fec59ceb9cbe6ec474c31c1dc5b66555b6', 
            value: '0x10', 
            data: '0x7f7465737432000000000000000000000000000000000000000000000000000000600057',
            chainId: 3
        },
        signedSample: {},
        recoveredAddress: ""
    },
    methods:{
        generateNew: function(){
            this.mnemonic = generateMnemonic()
        },
        signSampleTx: function(){
            this.signedSample = signTx(this.privKey, this.sampleTransaction)
            console.log("signed Sample", this.signedSample)
        }
    },
    watch: {
        mnemonic: function(val){
            this.privKey = generatePrivKey(val)
        },
        privKey: function(val){
            this.pubKey = derivePubKey(val)
        },
        pubKey: function(val){
            this.ETHaddress = deriveEthAddress(val)
            this.recoveredAddress = ""
        },
        signedSample: function(val){
            this.recoveredAddress = getSignerAddress(val)
        }
    }
})