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Create React App TypeScript: How to Enhance App Development

Would you like to add TypeScript to your web project built using React? TypeScript is a superset of JavaScript that add type checking on your codebase. This essentially acts as a first layer of protection that ensures you’re publishing error free code online. Integrating TypeScript to a React project is fairly straightforward, thanks to the create react app typescript package. In this tutorial, we’ll explain what TypeScript means and cover the basics of adding TypeScript support to React apps. We’ll show you how to do this in a fresh install and an existing React-based project to use Create React App Typescript.

Excited? Let’s jump right in!

Brief Overview of React

ReactJS is an open-source frontend Javascript library created by Facebook for creating user interfaces and components. Its core concept involves components – reusable and composable building blocks that allow developers to structure UIs efficiently.

React uses a declarative model, making it easier to understand and debug. It uses a component-based architecture, which makes it easy to build complex UIs from small, reusable pieces.

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Introduction to TypeScript

TypeScript is a superset of JavaScript, developed and maintained by Microsoft. It introduces static typing, allowing developers to specify data types within the codebase.

It builds upon JavaScript, providing additional functionalities while maintaining compatibility with existing JavaScript code.

TypeScript is particularly beneficial in building large-scale JavaScript applications because it enhances code maintainability and developer organization.

Benefits of Using TypeScript With React

Using TypeScript with React has some advantages that can help you enhance your App development process and improve your code quality. Below are some of the benefits of using Typescript with React:

Static Typing: Typescript introduces static typing to JavaScript. This feature allows developers to define types for variables, function parameters, and return values in React. Static typing helps the developer to catch type-related errors at compile-time rather than runtime, leading to more robust and predictable code.

Improved IDE Support: TypeScript enhances IDE support, offering features like IntelliSense and better code completion for JSX.

Getting Started With React and TypeScript

In this section, we’ll show you how to integrate TypeScript into an existing React app.

Prerequisites

To follow along with this guide, you’ll need to have the following in place:

  • Basic knowledge of React

  • Familiarity with TypeScript

  • Required software installations (Node.js, npm, etc.)

If you need a refresher on React, check out the video below.

Installation Process

For this tutorial, we’ll use create-react-app to install React on our local machine. To do so, run the command below.

npx create-react-app my-app

Using npx to install React ensures you have the latest version of the framework.

Once the installation is completed, navigate to your project directory by running the command cd my-app in the terminal window.

To add TypeScript support to an existing project, run the command below.

NPM:

npm install --save typescript @types/node @types/react @types/react-dom @types/jest

Yarn:

yarn add typescript @types/node @types/react @types/react-dom @types/jest

After installing the TypeScript dependencies, you’ll need to rename all the files with .js file extension to .ts. If you have files with .jsx extension, replace those with .tsx. This ensures all your project uses TypeScript files across the board.

Once done, restart your development server. You should now have TypeScript support on your app. TypeScript will flag type errors as you continue to develop your application.

Setting up Your First TypeScript React App

We’ve shown you how to add TypeScript support to an existing React application. This section will cover the steps to install TypeScript and React on a fresh install.

Creating a New App

To start a new React project with TypeScript, we’ll use the create-react-app package with a TypeScript template. For this, run the command below in your terminal window.

NPM:

npx create-react-app project-name --template typescript

Yarn:

yarn create react-app my-app --template typescript

Replace project-name with your desired name. This command sets up a new React project with TypeScript integration.

Explanation of the Folder Structure

After running the command, you will get a project directory that looks like this:

  • node_modules/: Contains all your npm dependencies.

  • public/: Public files like index.html, favicons, etc.

  • src/: Your source files, where you’ll spend most of your time.

    • App.tsx: The main React component file.

    • index.tsx: The entry point for your React app.

    • react-app-env.d.ts: Contains type declarations for your project.

    • reportWebVitals.ts: (Optional) For measuring performance.

  • package.json: Manages your project’s dependencies and scripts.

  • tsconfig.json: Configures your TypeScript compiler.

Understanding TypeScript in React

TypeScript in React adds static type checking to the components, props, state, and event handlers. This enhances the development experience through better error checking and more readable code.

Basic TypeScript Types Used in React

TypeScript introduces basic types like string, number, boolean, array, object, etc., and also specific types for React elements and events. Commonly used types in React include:

  • React.Element: Represents a React element.

  • React.ReactNode: A type that represents any possible return value of a component.

  • React.FC or React.FunctionComponent: A type for functional components.

  • React.ComponentType: A generic type for React components.

Differences in Component Creation with TypeScript

In TypeScript, components are defined with explicit props and state types, enhancing the code’s reliability.

Functional Component Example:

interface AppProps {
  title: string;
}

const App: React.FC<AppProps> = ({ title }) => {
  return <h1>{title}</h1>;
};

In this example, AppProps is an interface describing the shape of props that App component expects.

Class Component Example:

interface AppState {
  count: number;
}

class App extends React.Component<{}, AppState> {
  state: AppState = {
    count: 0,
  };

  // Component methods...
}

Here, AppState defines the type for the state of the App class component.

FeatureFunction-Based ComponentClass-Based Component
SyntaxSimpler, more concise syntax. Uses JavaScript functions.More verbose, uses ES6 classes.
State ManagementUses React Hooks (e.g., useState) for state management.Uses this.state and this.setState for managing state.
Lifecycle MethodsDoes not have lifecycle methods. Uses Hooks like useEffect for lifecycle events.Has lifecycle methods like componentDidMount, componentDidUpdate, etc.
TypeScript IntegrationProps are defined using type or interface and used directly in the function.Props and state types are defined as generic types in the class declaration.
this KeywordDoes not use this keyword. Functional components capture the props and state from the function scope.Requires use of this keyword to access props, state, and class methods.

Adding Types to Props and State

Props: Let’s define an interface or type for the props and then use this type to define the component’s props.

interface GreetingProps {
  name: string;
}

const Greeting: React.FC<GreetingProps> = ({ name }) => <div>Hello, {name}!</div>;

State: In class components, you can define the state structure using an interface or type.

interface AppState {
  count: number;
}

class Counter extends React.Component<{}, AppState> {
  state = {
    count: 0
  };

  increment = () => {
    this.setState(prevState => ({ count: prevState.count + 1 }));
  };

  render() {
    return (
      <div>
        <p>{this.state.count}</p>
        <button onClick={this.increment}>Increment</button>
      </div>
    );
  }
}

In this setup, TypeScript helps catch errors related to type mismatches and makes the code more predictable and easier to debug, particularly in large-scale applications.

Development with TypeScript in React

Now, you have a basic understanding of using TypeScript with React. Let’s explore some core concepts to help you get the most from this integration.

Building Components

Creating Functional Components with TypeScript: Functional components are simpler and generally preferred in modern React development. With TypeScript, you define the type of props the component expects.

Example:

interface GreetingProps {
  name: string;
}

const Greeting: React.FC<GreetingProps> = ({ name }) => {
  return <h1>Hello, {name}!</h1>;
};

In this example, GreetingProps is an interface that specifies the structure of the props object. React.FC<GreetingProps> is a generic type provided by React, indicating that Greeting is a functional component with props of type GreetingProps.

Creating Class Components with TypeScript: Class components are more verbose but useful for more complex components, especially those requiring lifecycle methods or state management.

Example:

interface CounterProps {
  initialCount: number;
}

interface CounterState {
  count: number;
}

class Counter extends React.Component<CounterProps, CounterState> {
  constructor(props: CounterProps) {
    super(props);
    this.state = { count: props.initialCount };
  }

  increment = () => {
    this.setState({ count: this.state.count + 1 });
  };

  render() {
    return (
      <div>
        <p>Count: {this.state.count}</p>
        <button onClick={this.increment}>Increment</button>
      </div>
    );
  }
}

Here, CounterProps and CounterState define the types for props and state, respectively.

Managing State and Props

In both functional and class components, you define types for props and state to leverage TypeScript’s type-checking.

For functional components, hooks like useState can infer types from the initial state or be explicitly set:

const [count, setCount] = useState<number>(0);

In class components, you define state types within the class signature and initialize state in the constructor:

state: CounterState = { count: 0 };

TypeScript with React Hooks

Using TypeScript with React Hooks enhances the development experience by providing type safety. This helps in catching errors early and makes the code more maintainable.

Below are detailed explanations and examples of using TypeScript with common React hooks like useState and useEffect, as well as custom hooks.

Using TypeScript with useState

The useState hook is used for state management in functional components. TypeScript can enforce the type of the state variable. Here is an example.

import React, { useState } from 'react';

const Counter: React.FC = () => {
  const [count, setCount] = useState<number>(0); // Specifying the type as number

  const increment = () => {
    setCount(count + 1);
  };

  return (
    <div>
      <p>{count}</p>
      <button onClick={increment}>Increment</button>
    </div>
  );
};

In this example, useState<number>(0) ensures that count is always a number, providing type safety for both the state variable count and the updater function setCount.

Using TypeScript with useEffect

The useEffect hook is used to perform side effects in functional components. TypeScript can be used to ensure the correctness of dependencies passed to it. Here is an example.

import React, { useState, useEffect } from 'react';

const Timer: React.FC = () => {
  const [seconds, setSeconds] = useState<number>(0);

  useEffect(() => {
    const interval = setInterval(() => {
      setSeconds(prevSeconds => prevSeconds + 1);
    }, 1000);

    return () => clearInterval(interval);
  }, []); // Empty dependency array

  return <p>{seconds} seconds have elapsed.</p>;
};

In this useEffect, TypeScript doesn’t enforce any specific type on the dependency array, but it helps ensure functions and variables used inside useEffect are of the correct type.

Using TypeScript with Custom Hooks

Custom hooks can also benefit from TypeScript’s type-checking. You can define the return type of the hook to ensure consistency and reliability. For example:

import { useState } from 'react';

function useToggle(initialValue: boolean): [boolean, () => void] {
  const [value, setValue] = useState<boolean>(initialValue);

  const toggle = () => {
    setValue(!value);
  };

  return [value, toggle];
}

export default useToggle;

In the useToggle custom hook, TypeScript specifies that the hook returns a tuple: the current state as a boolean and a function to toggle this state. This ensures that the consumers of the hook use it correctly.

Best Practices

When combining React with TypeScript, certain best practices can greatly enhance your development process, ensuring more robust, maintainable, and scalable applications. Let’s delve into the key areas of focus.

Structuring TypeScript React Projects

  1. Organize by Feature or Functionality: Structure your project by grouping related files (components, hooks, types) by feature or functionality. This approach, often referred to as “feature-based” or “module-based” structuring, enhances readability and maintainability.

  2. Use a Consistent Naming Convention: For instance, use .tsx for React components and .ts for non-component modules. Stick to a naming pattern for components and hooks that clearly signify their purpose and functionality.

  3. Centralize Type Definitions: Consider having a central file or directory (types.ts or types folder) for common type definitions. This approach is especially useful for large projects to maintain consistency in type definitions across different components and modules.

  4. Modularize Components and Logic: Break down complex components into smaller, reusable components and functions. This makes your components more manageable and facilitates easier testing and maintenance.

TypeScript-Specific Linting and Formatting

  1. Use ESLint with TypeScript: ESLint and the appropriate TypeScript plugins (@typescript-eslint/parser and @typescript-eslint/eslint-plugin), helps identify complex patterns in your code. This tool is crucial for maintaining code quality and consistency.

  2. Configure Prettier for Code Formatting: Prettier can work alongside ESLint to enforce a consistent code style. This setup helps avoid stylistic errors and ensures a uniform codebase, which is particularly beneficial for team collaborations.

  3. Utilize Editor Integrations: Most modern code editors (like VSCode) integrate with ESLint and Prettier. Utilize these integrations for real-time linting and formatting, which can significantly simplify your development process.

Tips for Effective Type-Checking

  1. Define Types for Props and State: Always declare explicit types for props and state in your components. This practice can catch potential bugs during development, reducing runtime errors.

  2. Use Utility Types for Flexibility: TypeScript provides utility types like Partial, Readonly, and Record. These types can be very handy in creating more flexible or constrained types depending on your use case.

  3. Avoid any Type: Using any type negates the benefits of TypeScript. Strive to use specific types. If a certain type is unknown or complex, consider using unknown or defining a more specific type.

  4. Gradual Typing for Legacy Projects: For existing projects migrating to TypeScript, start by enabling strict null checks and gradually add types to components. You can start with the most commonly used ones.

  5. Utilize Generic Types for Reusable Functions and Components: Generics allow you to create components and functions that work with various types rather than a single one.

Frequently Asked Questions

Below, we’ve answered some top questions developers ask about using TypeScript in a React app.

Can I use TypeScript with create-react-app?

Yes, you can use TypeScript with create-react-app. The tool supports TypeScript out of the box. You can bootstrap a TypeScript React project using the command: npx create-react-app my-app –template typescript.

Can existing React projects be migrated to TypeScript?

Yes, existing React projects can be gradually migrated to TypeScript. You can start by introducing TypeScript into your build toolchain and renaming your .js files to .tsx (for components) or .ts (for non-component files). Gradually, you can add type annotations and resolve any TypeScript errors.

How do you define types for props and state in functional components?

In functional components, props can be typed using TypeScript interfaces or types. For state within hooks like useState, you can either let TypeScript infer the type from the initial value or explicitly set the type.

interface Props {
  message: string;
}

const MyComponent: React.FC<Props> = ({ message }) => {
  const [count, setCount] = useState<number>(0); // Explicitly setting the type of state
  // Component logic...
};

What are some common TypeScript patterns used in React development?

  • Interface for Props and State: Defining interfaces for component props and state for better type-checking.

  • Generic Components: Using TypeScript generics to create components that work with different types.

  • Utility Types: Leveraging TypeScript utility types like Partial, Readonly, and Pick for more flexible type definitions.

  • Higher-Order Components: Typing higher-order components (HOCs) to add additional props or state to existing components.

  • Hooks with Types: Applying types in custom hooks for consistency and predictability.

Should You Use TypeScript With React?

Integrating your React app with TypeScript is a step in the right direction. It adds type-checking to your project, ensuring your codebase is error-free and maintainable.

In this tutorial, we’ve shown you how to create a React TypeScript app and the steps to optimize your code for better performance. You should be well on your way to enjoying the benefits TypeScript provides to React apps.

Building with React improves your development time. However, you can take it further and use some of PureCode AI’s ready-made templates. PureCode provides templates to cater to any component you intend to build on your app.

Checkout PureCode AI Templates

Further Reading:

If you enjoyed this post, check out others from our blog to help you become a better developer.

Check out the video below to learn more about using TypeScript with React. Happy Coding!

David Ozokoye

David Ozokoye

Software Engineer and Technical Writer