Type-Checking and Validation with TypeScript

In this chapter, we’ll explore the importance of property validation in React components for creating robust, bug-free applications. We’ll introduce TypeScript, which is a powerful tool for static type-checking in JavaScript.

We’ll guide you through setting up TypeScript in the project and cover its basic and advanced concepts. We’ll also provide examples of how to use TypeScript for type-checking in React components.

By the end of this chapter, you’ll have a solid foundation in property validation and type-checking, and be ready to create more predictable, reliable components using TypeScript.

The following topics will be covered in this chapter:

• Knowing what to expect
• An introduction to TypeScript
• Using TypeScript in React

Technical requirements

The code files for this chapter can be found on GitHub at https://github.com/PacktPublishing/React-and-React-Native-5E/tree/main/Chapter05.

Knowing what to expect

In any application, predictability is key. A predictable application behaves in expected ways, reducing bugs, improving user experience, and simplifying maintenance. When we talk about predictability in the context of React, we often refer to how components behave based on the props they receive. Props is short for properties and serves as the inputs to React components, determining their behavior and rendering. This is where the concept of props validation comes into play.

The importance of props validation

Props validation is a way to ensure that components receive the right type of data. It’s like a contract between components. When a component specifies the types of props it expects to receive, it makes a promise that it will behave in a certain way if it receives props of those types.

Props validation is crucial for a few reasons, as follows:

• It helps catch errors early in the development process: If a component receives a...

Introduction to TypeScript

As we embark on this journey to learn about type-checking and validation, let’s momentarily step away from React and React Native and turn our attention to TypeScript. You might be wondering, “What exactly is TypeScript?”

TypeScript is a statically typed superset of JavaScript, developed and maintained by Microsoft. This means that it adds additional features to JavaScript, one of the most significant being static typing. While JavaScript is dynamically typed, TypeScript introduces a type system that allows you to explicitly define the type of data that variables, function parameters, and function return values can have.

But don’t worry, TypeScript is completely compatible with JavaScript. In fact, any valid JavaScript code is also valid TypeScript code. TypeScript uses a transpiler (a type of compiler) to convert TypeScript code, which browsers can’t understand directly, into JavaScript code, which can run in any...

Using TypeScript in React

Alright, we’ve made it this far! We’ve learned about the basics of TypeScript and talked about its benefits. Now, it’s time to roll up our sleeves and get our hands dirty with some practical TypeScript in React.

In this section, we’re going to explore how to use TypeScript to type-check all the different parts of a React application. We’ll look at components, props, state, event handlers, context, and even refs. Don’t worry: I’ll walk you through plenty of examples to help illustrate these concepts.

Type-checking props in React components

In a React application, one of the primary areas where we can leverage TypeScript is in our components, specifically with props. Let’s see the example:

type GreetingProps = {
  name: string;
};
const Greeting = ({ name }: GreetingProps) => {
  return <h1>Hello, {name}!</h1>;
};

In this example, we’re defining a GreetingProps...

Summary

In this chapter, we delved into the world of type-checking and validation in React. We started with the importance of props validation, then introduced TypeScript and its benefits for robust type-checking.

We then applied TypeScript to React, demonstrating its use in type-checking various aspects of React components, from props and state to event handlers, context, and refs. All of it allows you to create applications that are not only more dependable but also easier to maintain, allowing for early detection of errors and significantly improving both the quality of your code and your efficiency as a developer.

As we move to the next chapter, Handling Navigation with Routes, we’ll shift our focus to navigation in React applications. We’ll learn how to set up and use routes to navigate between different parts of our application.