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React and React Native

React and React Native

By : Mikhail Sakhniuk, Roy Derks, Adam Boduch
4.3 (10)
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React and React Native

React and React Native

4.3 (10)
By: Mikhail Sakhniuk, Roy Derks, Adam Boduch

Overview of this book

Welcome to your big-picture guide to the React ecosystem. If you’re new to React and looking to become a professional React developer, this book is for you. This updated fifth edition reflects the current state of React, including React framework coverage as well as TypeScript. Part 1 introduces you to React. You’ll discover JSX syntax, hooks, functional components, and event handling, learn techniques to fetch data from a server, and tackle the tricky problem of state management. Once you’re comfortable with writing React in JavaScript, you’ll pick up TypeScript development in later chapters. Part 2 transitions you into React Native for mobile development. React Native goes hand-in-hand with React. With your React knowledge behind you, you’ll appreciate where and how React Native differs as you write shared components for Android and iOS apps. You’ll learn how to build responsive layouts, use animations, and implement geolocation. By the end of this book, you’ll have a big-picture view of React and React Native and be able to build applications with both.
Table of Contents (33 chapters)
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Part I: React
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Type-Checking and Validation with TypeScript
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8
Handling Navigation with Routes
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State Management in React
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Server-Side Rendering
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Unit Testing in React
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Part II: React Native
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29
Controlling Image Display
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31
Other Books You May Enjoy
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Index
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Unit testing

We already know that unit testing is the process of verifying the correctness of individual “units” of code: namely, functions and methods. The goal of unit testing is to ensure that each separate unit performs its task correctly, which, in turn, increases confidence in the reliability of the entire application.

export function sum(a: number, b: number): number {
  return a + b;
}
test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3);
});

The above represents the most basic and simplest test of a function that adds two values. The test code itself is a function that calls a special method, expect, which takes a value and then has a series of methods allowing for the checking and comparing of results.

Looking at this code, the first question that might come to mind is, is it really necessary to write another three lines of tests for such a simple three-line function? And why test such a function at all? I would answer...

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