main.js

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.hash = this.calculateHash();
    this.nonce = 0;
  }

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

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


class Blockchain {
  constructor() {
    this.chain = [this.createGenesisBlock()];
    this.difficulty = 4;
  }

  createGenesisBlock(){
    return new Block(0,"09/02/2018","Genesis Block","0");
  }

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

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

  isChainValid(){
    for(let i=1; i< this.chain.length; i++ ){
      const currentBlock = this.chain[i];
      const previousBlock = this.chain[i-1];

      if(currentBlock.hash !== currentBlock.calculateHash()){
        return false;
      }

      if(currentBlock.previousHash !== previousBlock.hash){
        return false;
      }

    }
      return true;
  }
}


let maverickcoin = new Blockchain();

console.log("Mining Block 1...");
maverickcoin.addBlock(new Block(1,"13/4/2018",{amount: 4}));
console.log("Mining Block 1...");
maverickcoin.addBlock(new Block(2,"12/4/2018",{amount: 10}));




// maverickcoin.chain[1].data = {amount: 100};
// maverickcoin.chain[1].hash = maverickcoin.chain[1].calculateHash();
// console.log("Is blockchain valid? " + maverickcoin.isChainValid());

//console.log(JSON.stringify(maverickcoin,null,4));