Book Image

Learn React with TypeScript 3

By : Carl Rippon
Book Image

Learn React with TypeScript 3

By: Carl Rippon

Overview of this book

React today is one of the most preferred choices for frontend development. Using React with TypeScript enhances development experience and offers a powerful combination to develop high performing web apps. In this book, you’ll learn how to create well structured and reusable react components that are easy to read and maintain by leveraging modern web development techniques. We will start with learning core TypeScript programming concepts before moving on to building reusable React components. You'll learn how to ensure all your components are type-safe by leveraging TypeScript's capabilities, including the latest on Project references, Tuples in rest parameters, and much more. You'll then be introduced to core features of React such as React Router, managing state with Redux and applying logic in lifecycle methods. Further on, you'll discover the latest features of React such as hooks and suspense which will enable you to create powerful function-based components. You'll get to grips with GraphQL web API using Apollo client to make your app more interactive. Finally, you'll learn how to write robust unit tests for React components using Jest. By the end of the book, you'll be well versed with all you need to develop fully featured web apps with React and TypeScript.
Table of Contents (14 chapters)

Testing pure functions

We'll start our unit testing journey in this section by implementing a unit test on a pure function.

A pure function has a consistent output value for a given set of parameter values. Pure functions only depend on the function arguments, and on nothing outside the function. These functions also don't change any of the argument values passed into them.

The fact that these functions only depend on their parameter values makes them straightforward to unit test.

We are going to implement a unit test on the required validator function we created in our Form component in the React shop we built. If you haven't already, open this project in Visual Studio Code.

We are going to use Jest, which is very popular for unit testing React apps, as our unit testing framework. Luckily the create-react-app tool installs and configures this for us when creating...