Let's build a blockchain

Proof of Work

    proofOfWork(difficulty) {
        const my = this;
        my.canceled = false;
        return new Promise((resolve, reject)=>{
            while (hash.substring(0, difficulty) !== Array(difficulty + 1).join("0")) {
                if (my.canceled) reject("Proof of Work aborted");
                my.nonce++;
                my.hash = this.computeHash();
                }
            resolve(my.hash);
            });
        }