concept of Blockchain in Javascript

blockchain.js

// A block is stored as a tuple of [parent_hash, transactions, hash_itself]

const {
	createHash,
} = require('crypto');

// get hash of some data
function hash(data) {
	return createHash('sha256').update(data).digest('hex');
}

// global chain
let chain = [];

// function to create a block
function create_block(transactions, parent_hash) {
	let hash_itself;
  
	if (Array.isArray(transactions))
		hash_itself = hash(transactions.join('').concat(parent_hash));
	else
		hash_itself = hash(transactions.concat(parent_hash));
	
  let block = [parent_hash, transactions, hash_itself];
	chain.push(block);
	
  return block;
}

// function to create the genesis block (first block)
function create_genesis_block(transactions) {
	let genesis_block = create_block(transactions, 0);
	
  chain = [genesis_block];
	
  return genesis_block;
}

let genesis_block = create_genesis_block("X paid $100 to Y")

genesis_block_hash = genesis_block[0];
// console.log("the hash of the genesis_block: ", genesis_block_hash);

let block1 = create_block(["Y paid $20 to Z", "X paid $10 to P"], genesis_block_hash);

console.log("Blockchain: ", chain);

/** Example output
Blockchain:  [
  [
    0,
    'X paid $100 to Y',
    '0ccc89g789bdf89gbmlf6knj5k6n75gkj6nk5j6gn5k6jng56jngyk98dgb8df89'
  ],
  [
    '0ccc89g789bdf89gbmlf6knj5k6n75gkj6nk5j6gn5k6jng56jngyk98dgb8df89',
    [ 'Y paid $20 to Z', 'X paid $10 to P' ],
    'iuuukjn45j6ng4j56nk5j6n45jg6n4kg5j6ng4j4ntgk4jn5gtjk4ntkj4ngtj45'
  ]
]
*/