Book Image

React Key Concepts

By : Maximilian Schwarzmüller
Book Image

React Key Concepts

By: Maximilian Schwarzmüller

Overview of this book

As the most popular JavaScript library for building modern, interactive user interfaces, React is an in-demand framework that’ll bring real value to your career or next project. But like any technology, learning React can be tricky, and finding the right teacher can make things a whole lot easier. Maximilian Schwarzmüller is a bestselling instructor who has helped over two million students worldwide learn how to code, and his latest React video course (React — The Complete Guide) has over six hundred thousand students on Udemy. Max has written this quick-start reference to help you get to grips with the world of React programming. Simple explanations, relevant examples, and a clear, concise approach make this fast-paced guide the ideal resource for busy developers. This book distills the core concepts of React and draws together its key features with neat summaries, thus perfectly complementing other in-depth teaching resources. So, whether you've just finished Max’s React video course and are looking for a handy reference tool, or you've been using a variety of other learning materials and now need a single study guide to bring everything together, this is the ideal companion to support you through your next React projects. Plus, it's fully up to date for React 18, so you can be sure you’re ready to go with the latest version.

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Table of Contents (16 chapters)
Preface
About the Book
Download A Free PDF Copy Of This Book
Free Chapter
1
1. React – What and Why
1. React – What and Why
Introduction
What Is React?
The Problem with "Vanilla JavaScript"
React and Declarative Code
Introducing Single Page Applications
Summary and Key Takeaways
2
2. Understanding React Components and JSX
2. Understanding React Components and JSX
Introduction
What Are Components?
What Does React Do with All These Components?
JSX vs HTML vs Vanilla JavaScript
Outputting Dynamic Content
Summary and Key Takeaways
Apply What You Learned
3
3. Components and Props
3. Components and Props
Introduction
Not There Yet
Using Props in Components
Components, Props, and Reusability
How to Deal with Multiple Props
Summary and Key Takeaways
Apply What You Learned
4
4. Working with Events and State
4. Working with Events and State
Introduction
What's the Problem?
Updating State Correctly
A Look under the Hood of React
Working with Multiple State Values
Deriving Values from State
Summary and Key Takeaways
Apply What You Learned
5
5. Rendering Lists and Conditional Content
5. Rendering Lists and Conditional Content
Introduction
What Are Conditional Content and List Data?
Rendering Content Conditionally
Outputting List Data
A Problem with List Items
Summary and Key Takeaways
Apply What You Learned
6
6. Styling React Apps
6. Styling React Apps
Introduction
How Does Styling Work in React Apps?
Scoped Styles with CSS Modules
Summary and Key Takeaways
Apply What You Learned
7
7. Portals and Refs
7. Portals and Refs
Introduction
A World without Refs
Refs versus State
Using Refs for More than DOM Access
React and Where Things End up in the DOM
Summary and Key Takeaways
Apply What You Have Learned
8
8. Handling Side Effects
8. Handling Side Effects
Introduction
What's the Problem?
Understanding Side Effects
Dealing with Side Effects with the useEffect() Hook
Effects and Their Dependencies
Summary and Key Takeaways
Apply What You Learned
9
9. Behind the Scenes of React and Optimization Opportunities
9. Behind the Scenes of React and Optimization Opportunities
Introduction
Revisiting Component Evaluations and Updates
The Virtual DOM vs the Real DOM
Avoiding Unnecessary Code Download
Strict Mode
Debugging Code and the React Developer Tools
Summary and Key Takeaways
Apply What You Learned
10
10. Working with Complex State
10. Working with Complex State
Introduction
A Problem with Cross-Component State
Using Context to Handle Multi-Component State
Limitations of useState( )
Managing State with useReducer( )
Summary and Key Takeaways
Apply What You Learned
11
11. Building Custom React Hooks
11. Building Custom React Hooks
Introduction
Why Would You Build Custom Hooks?
Custom Hooks: A Flexible Feature
A More Complex Example
Summary and Key Takeaways
Apply What You Learned
12
12. Multipage Apps with React Router
12. Multipage Apps with React Router
Introduction
One Page Is Not Enough
Getting Started with React Router and Defining Routes
From Static to Dynamic Routes
Redirecting
Summary and Key Takeaways
Apply What You Learned
13
13. Managing Data with React Router
13. Managing Data with React Router
Introduction
Data Fetching and Routing Are Tightly Coupled
Loading Data with React Router
Layouts Revisited
Handling Errors
Onward to Data Submission
Summary and Key Takeaways
Apply What You Learned
14
14. Next Steps and Further Resources
14. Next Steps and Further Resources
Introduction
How Should You Proceed?
Final Words
Appendix
2. Understanding React Components & JSX
3. Components & Props
4. Working with Events & State
5. Rendering Lists & Conditional Content
6. Styling React Apps
7. Portals & Refs
8. Handling Side Effects
9. Behind the Scenes of React & Optimization Opportunities
10. Working with Complex State
11. Building Custom React Hooks
12. Multipage Apps with React Router
13. Managing Data with React Router

Managing State with useReducer()

Just like useState(), useReducer() is a React Hook. And just like useState(), it is a Hook that can trigger component function re-evaluations. But, of course, it works slightly differently; otherwise, it would be a redundant Hook.

useReducer() is a Hook meant to be used for managing complex state objects. You will rarely (probably never) use it to manage simple string or number values.

This Hook takes two main arguments:

  • A reducer function
  • An initial state value

This brings up an important question: what is a reducer function?

Understanding Reducer Functions

In the context of useReducer(), a reducer function is a function that itself receives two parameters:

  • The current state value
  • An action that was dispatched

Besides receiving arguments, a reducer function must also return a value: the new state. It's called a reducer function because it reduces the old state (combined with an action) to a new...

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