Blockchain.prototype.createNewBlock = function(nonce, prevBlockHash, hash){
const newBlock = {
index : this.chain.length + 1,
timestamp : Date.now(),
transactions : this.pendingTransactions,
nonce : nonce,
prevBlockHash : prevBlockHash,
hash : hash
};
this.pendingTransactions = [];
this.chain.push(newBlock);
return newBlock;
}