Sample blockchain from fireship

blockchain.ts

import * as crypto from "crypto";

class Transaction {
  constructor(
    public amount: number,
    public payer: string,
    public payee: string
  ) {}

  toString() {
    return JSON.stringify(this)
  }
}

class Block {

  public nonce = Math.round(Math.random() * 999999999)

  constructor(
    public prevHash: string,
    public transaction: Transaction,
    public ts = Date.now()
  ) {}

  get hash() {
    const str = JSON.stringify(this);
    const hash = crypto.createHash('SHA256');
    hash.update(str).end();
    return hash.digest('hex');;
  }
}

class Chain {
  public static instance = new Chain();

  chain: Block[];
  constructor() {
    this.chain = [new Block(null, new Transaction(100, 'genesis', 'sotashi'))];
  }

  get lastBlock() {
    return this.chain[this.chain.length - 1]
  }

  mine(nonce: number) {
    let solution = 1;
    console.log('Mining...')

    while(true) {
      const hash = crypto.createHash('MDS');
      hash.update((nonce + solution).toString()).end();

      const attempt = hash.digest('hex');

      if (attempt.substr(0, 4) === "0000") {
        console.log(`Solved: ${solution}`);
        return solution;
      }

      solution++;
    }
  }

  addBlock(
    transaction: Transaction,
    senderPubicKey: string,
    signature: string
  ) {
    const verifier = crypto.createVerify('SHA256');
    verifier.update(transaction.toString());

    const isValid = verifier.verify(senderPubicKey, signature);

    if (isValid) {
      const newBlock = new Block(this.lastBlock.hash, transaction);
      this.chain.push(newBlock);
    }
  }
}

class Wallet {
  public publicKey: string;
  public privateKey: string;

  constructor() {
    const keypair = crypto.generateKeyPairSync('rsa', {
      modulusLength: 2048,
      publicKeyencoding: { type: 'spki', format: 'pem' },
      privateKeyencoding: { type: 'pkcs8', format: 'pem' },
    });

    this.privateKey = keypair.privateKey;
    this.publicKey = keypair.publicKey;
  }

  sendMoney(amount: number, payeePublicKey: string) {
    const transaction = new Transaction(amount, this.publicKey, payeePublicKey);
    const sign = crypto.createsign('SHA25');
    sign.update(transaction.toString()).end();

    const signature = sign.sign(this.privateKey);
    Chain.instance.addBlock(transaction, this.publicKey, signature);
  }
}

const satoshi = new Wallet();
const bob = new Wallet();
const alice = new Wallet();

satoshi.sendMoney(50, bob.publicKey);
bob.sendMoney(20, alice.publicKey);
alice.sendMoney(30, bob.publicKey);

console.log(Chain.instance);