SimpleBlockchain.js

const sha256 = require('sha256');

class Block {
  constructor(index, timestamp, data, prevHash) {
    this.index = index;
    this.timestamp = timestamp;
    this.data = data;
    this.prevHash = prevHash;
    this.thisHash = sha256(
      this.index + this.timestamp + this.data + this.prevHash
    );
  }
}

const createGenesisBlock = () => new Block(0, Date.now(), 'Genesis Block', '0');

const nextBlock = (lastBlock, data) =>
  new Block(lastBlock.index + 1, Date.now(), data, lastBlock.thisHash);

const createBlockchain = num => {
  const blockchain = [createGenesisBlock()];
  let previousBlock = blockchain[0];

  for (let i = 1; i < num; i += 1) {
    const blockToAdd = nextBlock(previousBlock, `This is block #${i}`);
    blockchain.push(blockToAdd);
    previousBlock = blockToAdd;
  }
  console.log(blockchain);
};

const lengthToCreate = 20;
createBlockchain(lengthToCreate);