cryptocurrency-concept

Installation

1) git clone https://github.com/sarthaksadh01/cryptocurrency-concept-in-javascript.git
2) cd cryptocurrency-concept-in-javascript
3) npm install
4) npm start

Features

1) Adding transaction
2) Mining
3) Is Chain Valid
4) Replace chain (if longer chain exist)
5) Adding nodes 
6) Get Connected Nodes
7) Getting your Chain

definition

class BlockChain {

    constructor(myWallet) {
        this.nodes = new Set();
        this.transactions = [];
        this.chain = [];
        this.createBlock()
        this.myWallet = myWallet
    }

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

    getChain() {
        return this.chain;
    }

    getAllTransactions() {
        return this.transactions
    }
    getAllConnectedNodes(){
        return this.nodes;
    }


    isChainValid(chain=this.chain) {
        for (var i = 1; i < chain.length; i++) {
            if (chain[i].prevHash != chain[i - 1].hash) {
                return false;
            }

        }
        return true;
    }

    createBlock(nonce = 1, prevHash = '0'.repeat(64), transactions = [], hash = sha256('1' + "randomData" + '0' + '0')) {

        this.chain.push({
            nonce,
            index: this.chain.length,
            transactions,
            prevHash,
            hash,
            timeStamp: Date().toString()
        })

    }


    async addTransaction(sender = "", receiver = "", coins = 0, fees = 0.1) {
        var uid = await uidgen.generate();
        this.transactions.push(
            {
                sender,
                receiver,
                coins,
                fees,
                uid
            }
        )


    }

    replaceChain(){
        var longestChain = this.chain
        this.nodes.forEach((node)=>{

            var chain = request.get(node);
            var chainLength = chain.length;
            if(this.isChainValid(chain)&&chainLength>longestChain.length){
                longestChain=chain;
                this.chain=chain;
            }
            

        });
    }



    addNodes(node) {
        this.nodes.add(node);
    }


    mineBlock(difficulty = 4) {
        var index = this.chain.length;
        var prevBlock = this.chain[index - 1];
        var nonce = 1;
        if(this.transactions.length==1&&this.transactions[0].fees==0)return;
        console.log("mining block -- " + index);
        var hash = sha256(this.transactions + prevBlock.hash + index + nonce)
        while (hash.substring(0, difficulty) != '0'.repeat(difficulty)) {
            nonce += 1;
            hash = sha256(this.transactions + prevBlock.hash + index + nonce);
        }
        this.createBlock(nonce, prevBlock.hash, this.transactions, hash);
        this.transactions = [{
            "sender":"scoin",
            "receiver":this.myWallet,
            "coins":0.1,
            
        }];


    }



}