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main.js
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main.js
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const SHA256 = require('crypto-js/sha256');
class Transaction{
constructor(fromAddress, toAddress, amount){
this.fromAddress = fromAddress;
this.toAddress = toAddress;
this.amount = amount;
}
}
class Block{
constructor(timestamp, transactions, previousHash = ''){
this.timestamp = timestamp;
this.transactions = transactions;
this.previousHash = previousHash;
this.hash = this.claculateHash();
this.nonce = 0;
}
// creating a new method. this function will calculate the hash of the block.
claculateHash(){
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.claculateHash();
}
console.log("Block mined: " + this.hash);
}
}
// creating a new class for the blockchain.
class Blockchain{
constructor(){
this.chain = [this.createGenesisBlock()];
this.difficulty = 2;
this.pendingTransactions = [];
this.miningReward = 100;
}
// the first block in a blockchain is called the genesis block and it is added manually so create a method for that.
createGenesisBlock(){
// the genesis block is the first block in the chain and it has no previous hash.
return new Block("17/11/2023", "Genesis block", "0");
}
// to return the latest block in the chain.
getLatestBlock(){
return this.chain[this.chain.length - 1];
}
minePendingTransactions(miningRewardAddress){
let block = new Block(Date.now(), this.pendingTransactions);
block.mineBlock(this.difficulty);
console.log("Block successfully mined.............");
this.chain.push(block);
this.pendingTransactions = [
new Transaction(null, miningRewardAddress, this.miningReward)
];
}
createTransaction(transaction){
this.pendingTransactions.push(transaction);
}
getBalanceOfAddress(address){
let balance = 0;
for(const block of this.chain){
for(const trans of block.transactions) {
if(trans.fromAddress === address) {
balance -= trans.amount;
}
if(trans.toAddress === address) {
balance += trans.amount;
}
}
}
return balance;
}
// to check if the chain is valid or not.
isChainVaild(){
for(let i = 1; i < this.chain.length; i++){
const currentBlock = this.chain[i];
const previousBlock = this.chain[i - 1];
if(currentBlock.hash !== currentBlock.claculateHash()){
return false;
}
if(currentBlock.previousHash !== previousBlock.hash){
return false;
}
}
return true;
}
}
// creating a new instance of the blockchain.
let lynk4coin = new Blockchain();
// console.log('Mining block 1..........');
// lynk4coin.addBlock(new Block(1, "18/11/2023", {amount: 18}));
// console.log('Mining block 2..........');
// lynk4coin.addBlock(new Block(2, "19/11/2023", {amount: 19}));
// // let's see how the block chain looks like.
// console.log(JSON.stringify(lynk4coin, null, 4));
// console.log('Is Block Chain Valid?.......... '+ lynk4coin.isChainVaild());
// // lynk4coin.chain[1].data = {amount: 100};
lynk4coin.createTransaction(new Transaction('address1', 'address2', 100));
lynk4coin.createTransaction(new Transaction('address2', 'address2', 50));
console.log('\n Starting the miner..........');
lynk4coin.minePendingTransactions('lynk-address');
console.log('\n Balance of lynk is ', lynk4coin.getBalanceOfAddress('lynk-address'));
console.log('\n Starting the miner again..........');
lynk4coin.minePendingTransactions('lynk-address');
console.log('\n Balance of lynk is ', lynk4coin.getBalanceOfAddress('lynk-address'));