Adding A Block In Blockchain Using Javascript

mineBlock(difficulty) {
 while (this.hash.toString().substring(0, difficulty) !== Array(difficulty + 1).join("0")) {
  this.nonce++;
  this.hash = this.calculateHash();
 }
 console.log("Block Successfully hashed: " + this.hash);
 console.log("Nonce: " + this.nonce);
}

const SHA256 = require('crypto-js/sha256');

class Block {
 constructor(index, timestamp, data, previousHash) {
  this.index = index;
  this.timestamp = timestamp;
  this.data = data;
  this.previousHash = previousHash;
  this.nonce = 0;
  this.hash = this.calculateHash();
 }

 calculateHash() {
  return SHA256(this.index + this.previousHash + this.timestamp + JSON.stringify(this.data) + this.nonce);
 }

 mineBlock(difficulty) {
  while (this.hash.toString().substring(0, difficulty) !== Array(difficulty + 1).join("0")) {
   this.nonce++;
   this.hash = this.calculateHash();
  }
  console.log("Block Successfully hashed: " + this.hash);
  console.log("Nonce: " + this.nonce);
 }
}

class Blockchain {
 constructor() {
  this.chain = [this.createGenesisBlock()];
  this.difficulty = 3;
 }

 createGenesisBlock() {
  return new Block(0, '02/05/2020', 'Genesis Block', "0");
 }

 getlatestBlock() {
  return this.chain[this.chain.length - 1];
 }

 addBlock(newBlock) {
  newBlock.previousHash = this.getlatestBlock().previousHash;
  //newBlock.hash = newBlock.calculateHash();
  newBlock.mineBlock(this.difficulty);
  this.chain.push(newBlock);
 }
}

let demoChain = new Blockchain();

console.log("Starting................");

demoChain.addBlock(
 new Block(1, '02/05/2020', {
  amount: 10
 }));

console.log("Secondly................");

demoChain.addBlock(
 new Block(2, '02/05/2020', {
  amount: 25
 }));

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