simpleblockchainjs/app.js

A simple example of a working model of blockchain.

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();
    }

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

class BlockChain {
    constructor() {
        this.chain = [this.createGenesisBlock()];
    }

    createGenesisBlock() {
        return new Block(0, new Date().toISOString(), "Genesis Block", "0");
    }

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

    addBlock(newBlock) {
        newBlock.previousHash = this.getLatestBlock().hash;
        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 vickylanceCoin = new BlockChain();
vickylanceCoin.addBlock(new Block(vickylanceCoin.chain.length, new Date().toISOString(), { amount: 4 }));
vickylanceCoin.addBlock(new Block(vickylanceCoin.chain.length, new Date().toISOString(), { amount: 10 }));

// console.log(new Date().toISOString());
console.log('====================================');
console.log(JSON.stringify(vickylanceCoin, null, 4));
console.log('====================================');