Book Image

Building Enterprise JavaScript Applications

By : Daniel Li
Book Image

Building Enterprise JavaScript Applications

By: Daniel Li

Overview of this book

With the over-abundance of tools in the JavaScript ecosystem, it's easy to feel lost. Build tools, package managers, loaders, bundlers, linters, compilers, transpilers, typecheckers - how do you make sense of it all? In this book, we will build a simple API and React application from scratch. We begin by setting up our development environment using Git, yarn, Babel, and ESLint. Then, we will use Express, Elasticsearch and JSON Web Tokens (JWTs) to build a stateless API service. For the front-end, we will use React, Redux, and Webpack. A central theme in the book is maintaining code quality. As such, we will enforce a Test-Driven Development (TDD) process using Selenium, Cucumber, Mocha, Sinon, and Istanbul. As we progress through the book, the focus will shift towards automation and infrastructure. You will learn to work with Continuous Integration (CI) servers like Jenkins, deploying services inside Docker containers, and run them on Kubernetes. By following this book, you would gain the skills needed to build robust, production-ready applications.
Table of Contents (26 chapters)
Title Page
Copyright and Credits
Dedication
Packt Upsell
Contributors
Preface
Free Chapter
1
The Importance of Good Code
Index

Moving common logic into middleware


Let's see how we can improve our code further. If you examine our Create User endpoint handler, you may notice that its logic could be applied to all requests. For example, if a request comes in carrying a payload, we expect the value of its Content-Type header to include the string application/json, regardless of which endpoint it is hitting. Therefore, we should pull that piece of logic out into middleware functions to maximize reusability. Specifically, these middleware should perform the following checks:

  • If a request uses the method POSTPUT or PATCH, it must carry a non-empty payload.
  • If a request contains a non-empty payload, it should have its Content-Type header set. If it doesn't, respond with the 400 Bad Request status code.
  • If a request has set its Content-Type header, it must contain the string application/json. If it doesn't, respond with the 415 Unsupported Media Type status code.

 

Let's translate these criteria into Cucumber/Gherkin specifications...