Technology is constantly evolving, and blockchain is taking development to new places, as mobile did a decade ago – and Ethereum is the leading platform for creating this new wave of applications. This book reveals everything you need to create a robust decentralized application (more commonly known as DApp). Unlike other books on the topic, this one focuses on the web application layer, and guides you in creating great experiences on top of the Ethereum blockchain. You’ll review the challenges and differences involved in developing DApps as opposed to traditional web applications.

After a brief introduction to blockchain history and Ethereum in particular, you’ll jump directly into building a sample decentralized application, to familiarize yourself with all the moving pieces. This book offers specific chapters on querying and rendering data from the blockchain, reacting to events, interacting with user accounts, sending transactions, managing gas, handling confirmations and reorganizations, and more. You will also find a chapter dedicated to Solidity that will give you the necessary means to understand and even build your own smart contracts.

Other important topics covered include building backend servers that act as indexing layers, and managing storage efficiently with solutions like the interplanetary file system, or IPFS. Last but not least, you will find chapters that examine the biggest problems on Ethereum today: onboarding and scalability. These include the state of the art of the available strategies to tackle them, such as meta-transactions, smart accounts, ENS, state channels, sidechains, and more.

What You'll Learn

• Connect to the blockchain from the browser and send transactions from client-side
• Build a web app that provides a read-only interface to a blockchain contract
  
• Create a wallet interface for arbitrary fungible tokens, displaying the user’s balance and allowing for simple transfers to other addresses
• Develop a web app that stores large blobs of data off-chain, and keeps a reference to it on-chain (e.g. avatars, long text descriptions)
• Produce a web app that relies on a centralized server for indexing on-chain information to be presented to the user

Who This Book Is For

Web developers focused on client-side applications, with knowledge of JavaScript and HTML/CSS. You do not need any prior knowledge of Blockchain, Ethereum, or cryptocurrency.

技术在不断发展，区块链正将开发带到新的地方，就像十年前的移动通信一样--而以太坊是创建这一新一波应用的领先平台。本书揭示了创建一个强大的去中心化应用程序（更常被称为DApp）所需的一切。与其他相关书籍不同的是，这本书专注于网络应用层，并指导你在以太坊区块链的基础上创造伟大的体验。你将回顾开发DApp相对于传统网络应用的挑战和差异。

在简单介绍了区块链历史，特别是以太坊之后，你将直接跳到构建一个去中心化的样本应用程序，以熟悉所有的移动部件。本书提供了关于从区块链查询和渲染数据、对事件作出反应、与用户账户互动、发送交易、管理气体、处理确认和重组等具体章节。你还会发现有一章专门讨论Solidity，它将为你提供必要的手段来理解甚至建立你自己的智能合约。

涵盖的其他重要主题包括构建作为索引层的后端服务器，以及利用行星间文件系统或IPFS等解决方案有效管理存储。最后但并非最不重要的是，你会发现一些章节研究了当今以太坊上最大的问题：入驻和可扩展性。这包括解决这些问题的现有策略的技术水平，如元交易、智能账户、ENS、状态通道、侧链等。

你会学到什么

从浏览器连接到区块链并从客户端发送交易

构建一个网络应用，为区块链合约提供一个只读的接口

为任意可替换的代币创建一个钱包界面，显示用户的余额并允许简单地转移到其他地址

开发一个网络应用程序，在链外存储大量的数据，并在链上保持对它的引用（如头像、长文本描述）。

制作一个网络应用，依靠一个集中的服务器来索引链上的信息，并呈现给用户。

本书适用对象

专注于客户端应用的网络开发人员，具有JavaScript和HTML/CSS知识。你不需要任何关于区块链、以太坊或加密货币的知识。