Book Image

Learn Blockchain Programming with JavaScript

By : Eric Traub
Book Image

Learn Blockchain Programming with JavaScript

By: Eric Traub

Overview of this book

Learn Blockchain Programming with JavaScript begins by giving you a clear understanding of what blockchain technology is. You’ll then set up an environment to build your very own blockchain and you’ll add various functionalities to it. By adding functionalities to your blockchain such as the ability to mine new blocks, create transactions, and secure your blockchain through a proof-of-work you’ll gain an in-depth understanding of how blockchain technology functions. As you make your way through the chapters, you’ll learn how to build an API server to interact with your blockchain and how to host your blockchain on a decentralized network. You’ll also build a consensus algorithm and use it to verify data and keep the entire blockchain network synchronized. In the concluding chapters, you’ll finish building your blockchain prototype and gain a thorough understanding of why blockchain technology is so secure and valuable. By the end of this book, you'll understand how decentralized blockchain networks function and why decentralization is such an important feature for securing a blockchain.
Table of Contents (10 chapters)

Building the chainIsValid method

Let's start building the consensus algorithm by creating a new method called chainIsValid. This method will validate whether or not a chain is legitimate. Let's get started with building this method:

  1. In the blockchain.js file, after the proofOfWork method, let's define the method as follows:
Blockchain.prototype.chainIsValid = function() {

}
  1. Now, this method will take in a blockchain as an argument, and will return to us whether the blockchain is valid or not:
Blockchain.prototype.chainIsValid = function(blockchain) {

}

We're going to use this chainIsValid method to validate the other chains inside of the network when we are comparing them to the chain that is hosted on the current node. In order to validate that the blockchain is legitimate, we're simply going to iterate through every block inside of the blockchain...