How This Book Is Structured

What's the point of React?

Lesson 0 - Object Elements

Lesson 1 - Element Factory

Lesson 2 - JSX

Lesson 3 - Nested Elements

Lesson 4 - Components

Lesson 5 - Props

Lesson 6 - Prop Types

Lesson 7 - Nested Components

Lesson 8 - Class Components

Lesson 9 - Lifecycle Methods

Lesson 10 - Example App

Lesson 11 - More Lifecycle Methods

Lesson 12 - Refactoring Components

Lesson 14 - Refs

Lesson 15 - Simple Integration

Lesson 16 - Advanced Integration

Lesson 18 - ES215

Virtual DOM Primer

Changelog

A gentle introduction to React, using the JavaScript you already know

React from Zero

Now that we know how to use props in our custom components, it would be nice to prevent users of these components from using invalid values. That is, a certain prop may only work properly if it is passed a 

There exist multiple solutions for this problem, like 

, but those solutions involve essentially using another programming language which requires a compile-to-Javascript step, which is something we'd like to avoid.

Instead of checking the types of the props at compile time, we can implement a solution in JavaScript by checking at 

. React has a library for type checking at run time called 

# Lesson 6 - Prop Types

Now that we know how to use props in our custom components, it would be nice to prevent users of these components from using invalid values. That is, a certain prop may only work properly if it is passed a `String` or a `Component`.

There exist multiple solutions for this problem, like [static typing](https://stackoverflow.com/questions/1517582/what-is-the-difference-between-statically-typed-and-dynamically-typed-languages) with [Flow](https://flow.org/) or [TypeScript](https://www.typescriptlang.org/), but those solutions involve essentially using another programming language which requires a compile-to-Javascript step, which is something we'd like to avoid.

Instead of checking the types of the props at compile time, we can implement a solution in JavaScript by checking at _runtime_. React has a library for type checking at run time called **prop types**.

Kay Plößer