ReactJS

Getting Started with React and TypeScript

Published Jan 27, 2021

Updated Feb 14, 2023

7 min read

This article was written over 18 months ago and may contain information that is out of date. Some content may be relevant but please refer to the relevant official documentation or available resources for the latest information.

Getting Started with React and TypeScript

React and TypeScript makes for a fantastic combination when it comes to developing web sites and web applications. With React's focus on creating a fantastic user interface and TypeScript's ability to type check our code, it's never been easier to sanely develop a fantastic user experience.

Prerequisites

Before getting started, you'll need NodeJS and NPM installed. Go here to find instructions on how to install it on your computer.

You should also have a bit of knowledge in using React. If not, I highly recommend getting started learning React using vanilla JavaScript.

Create React App

Facebook's Create-React-App is a preview of the wonderful development experience React has to offer. It will enable us to start writing code immediately.

Check out their documentation here if you have any questions or want to dive in a touch deeper on how the tool works.

In summary, Create-React-App will set up a complete development environment for us. It will configure and conceal build tool configurations for us so that all we need to focus on is our code. Here is some of the tooling that CRA (create-react-app) sets up for us:

Let's use this tool now to create our TypeScript/React development environment. Use the following command to generate a new Typescript React App.

npx create-react-app my-app --template typescript

If you use yarn, use the following command:

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

After the tool has finished running, switch directories into my-app run the command npm start to spin up your development environment. Once it's done loading, we should see localhost:3000 open up.

Folder Structure

Create-react-app scaffolds out the folder structure of your app for us, minimizing the amount of code you need to write to go from idea to production.

Here are some important files to take note of:

public/index.html - This is the HTML file that consumes the bundle generated by Create-React-App's hidden tooling.
src/index.tsx - This is the TypeScript entry point file. All of the project's dependencies are mapped out by Webpack (all set up for us invisibly by CRA) using this file. The bundle generated is injected into public/index.html. This file has a few responsibilities. The most important are:
- import our main React component
- Render that App component to the DOM using ReactDom.render()
src/App.tsx - This is our main React Component. The .tsx extension tells us that the file uses both TypeScript and JSX. This is the main component in our app which is rendered to the DOM by ReactDOM. We'll spend most of our time in this file getting the hang of writing React code using TypeScript.
tsconfig.json - This is the TypeScript configuration file. This file was generated for us by Create-React-App and we can freely edit this configuration to best suit our needs.

Hello, World - With TypeScript and React

Let's get to coding.

To keep things organized, make a new folder src/components and create our new component, src/components/HelloWorld.tsx. In this file, we'll write just 2 lines of code:

const HelloWorld = () => <h1>Hello, World!</h1>
export default HelloWorld

The first line defines our new component. It's simply a function that returns some JSX. In this case, it's our "Hello, World!" heading tag. The second line exports the component, allowing other modules to import it.

To import and use this component, load up src/App.tsx and do the following:

Include import HelloWorld from './components/HelloWorld' at the very top of the file to import the component
Use the component by having the App component return some JSX which includes <HelloWorld />.

After some refactoring, your App.tsx might look something like this:

import './App.css';
import HelloWorld from './components/HelloWorld'

const App = () => {
  return (
    <div className="App">
      <HelloWorld />
    </div>
  );
}

export default App;

In the above example, I've left the default styles, imported our HelloWorld component, and refactored the JSX which is returned by App so it includes <HelloWorld />.

Adding a bit of TypeScript

Let's increase the safety of our code by using some TypeScript features.

This is what our src/components/HelloWorld.tsx looks like right now:

const HelloWorld = () => <h1>Hello, World!</h1>
export default HelloWorld

A huge benefit of TypeScript is that it can help us catch errors before you run your code instead of at run-time. Let's introduce a bug to our code:

Refactor our HelloWorld component so it looks like this:

const HelloWorld = () => "Hello, World!"
export default HelloWorld

This is valid JavaScript, but not valid React. A functional component must return JSX (or null). It can't just return a string. We're made aware of this error when Create-React-App tries to build our code.

Let's refactor our code to use some TypeScript features so our editor notices the error:

import { FC } from 'react'
const HelloWorld: FC = () => "Hello, World!"
export default HelloWorld

The import statement imports the FunctionComponent type FC, and allows us to type our functional component to ensure it returns valid JSX. By typing the function, our editor can now immediately show us our error. Click here for more information on typing functions in TypeScript.

TypeScript is explicitly telling us that we can't assign a return type of string to our functional component. Now that TypeScript has shown us this error, let's correct it.

import { FC } from 'react'
const HelloWorld: FC = () => <h1>Hello, World!</h1>
export default HelloWorld

By fixing our function and returning JSX, HelloWorld now passes TypeScript's type checks and no error is thrown. As a result, our project builds and works once more.

Benefits of TypeScript

As shown in the previous example, TypeScript can help us catch errors before we even leave our code editor. This results in faster development since TypeScript will be actively debugging your code as you write. Better to catch silly errors immediately than insanity-inducing errors during run-time.

Let's show another example of how enforcing types can help us catch errors early.

We'll create a new React component, List. This new component will take an array of string data as a prop and return some JSX which renders a <ul> tag and iterate over the list of data, rendering an <li> for each piece of data.

Here is what my version of this component could look like with more type safety from TypeScript included.

src/components/List.tsx

import { FC } from 'react'

const List: FC<{ data: string[] }> = ({ data }) => (
  <ul>
    {data.map(item => <li>{item}</li>)}
  </ul>
)

export default List

Just like our previous example, we import FC from react and use it to type our function. What we're also doing is defining a type for our data prop. In this example, we are saying that data is an array of strings. Notice how self-documenting that is. This is a huge benefit of TypeScript.

Now let's insert this component into src/App.tsx, pass into it an array of data, and sprinkle in a bit more TypeScript.

src/App.tsx

import './App.css';
import { FC } from 'react'
import HelloWorld from './components/HelloWorld'
import List from './components/List'

const avengers = [
  'Captain America',
  'Iron Man',
  'Black Widow',
  'Thor',
  'Hawkeye',
]

const App: FC = () => {
  return (
    <div className="App">
      <HelloWorld />
      <List data={avengers} />
    </div>
  );
}

export default App;

We created an avengers array, with 5 members of the Avengers team. We then passed in this list of data as a property to List. This example works because we defined List to accept an array of strings. Let's trigger a TypeScript error and send it a more varied array.

import './App.css';
import { FC } from 'react'
import HelloWorld from './components/HelloWorld'
import List from './components/List'

const avengers = [
  'Captain America',
  'Iron Man',
  'Black Widow',
  'Thor',
  'Hawkeye',
  {
    name: 'Vision',
  },
  {
    name: 'Hulk',
    color: 'green',
  },
]

const App: FC = () => {
  return (
    <div className="App">
      <HelloWorld />
      <List data={avengers} />
    </div>
  );
}

export default App;

We added 2 new heroes to the avengers array, Vision and the Hulk, but we added them as objects, not as strings. This causes TypeScript to throw an error.

TypeScript is telling us that our data doesn't fit the definition of the data prop. It even points out to us exactly where this prop is defined. Let's assume that we should be sending an array of objects instead of strings. Let's refactor our files so everything works again.

src/App.tsx

import './App.css';
import { FC } from 'react'
import HelloWorld from './components/HelloWorld'
import List from './components/List'

const avengers = [
  { name: 'Captain America' },
  { name: 'Iron Man' },
  { name: 'Black Widow' },
  { name: 'Thor' },
  { name: 'Hawkeye' },
  { name: 'Vision' },
  { name: 'Hulk' },
]

const App: FC = () => {
  return (
    <div className="App">
      <HelloWorld />
      <List data={avengers} />
    </div>
  );
}

export default App;

src/components/List.tsx

import { FC } from 'react'

const List: FC<{ data: { name: string }[] }> = ({ data }) => (
  <ul>
    {data.map(({ name }) => <li>{name}</li>)}
  </ul>
)

export default List

We changed our List component definition and explicitly typed the data prop to be an array of objects containing a string type name property. By explicitly typing our data prop, we know its exact shape and can catch if we send this component any prop that is shaped differently than this.

Conclusion

By adding a type layer over JavaScript, TypeScript successfully saves developers time and frustration, even giving us a hand in self-documenting our code. While there surely is much more left to learn in typing your React applications, this should be a good platform to begin wading into the deep end of the pool, so to speak.

Happy coding!

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About the author(s)

Matthew Pagan
@mastapegs @mastapegs

Improving INP in React and Next.js

Improving INP in React and Next.js In one of my previous articles, I've explained what INP is, how it works, and how it may affect your website. I also promised you to follow up with more concrete advice on how to improve your INP in your favorite framework. This is the follow-up article, where I'll focus on how to improve your INP score in React and Next.js. How to prepare for INP in React and Next.js? The first thing to do is to ensure you're using the latest version of React. The React team has been working on making React more INP-friendly and has already made some improvements in the latest versions. To enhance your INP score, consider fully taking advantage of new features introduced in React 18, such as Concurrent Rendering, Automatic Batching, and Selective Hydration. However, there are also some general areas to focus on, such as SSR and SSG in Next.js, Web Workers, or optimizing your hooks and state management. Concurrent Rendering The Concurrent Mode in React uses an algorithm that breaks rendering down into so-called "fiber nodes" and schedules the renders based on their expiration and priority. This effectively allows the user to interact with the page while the rendering is still in progress. In previous React versions, all updates, such as setState calls were treated as "urgent" and once the re-render had started, there was no way to interrupt it. Concurrent Mode changes this by being able to prioritize the updates and interrupt a non-blocking state update started with startTransition. For a simple explanation of concurrency in React, you can check out Dan Abramov's explanation. As part of the Concurrent Mode, React introduced several lifecycle methods that allow you to prioritize the rendering of certain parts of your UI, such as: - useTransition hook that allows you to update the state without blocking the UI, - useDeferredValue hook that allows you to defer the rendering of certain parts of your UI, - startTransition API that, similarly to the useTransition hook lets you mark a state update as non-blocking. It lacks, however, an indication of whether it's still pending. Automatic Batching Introduced in React 18, Automatic Batching reduces the number of re-renders that happen on state changes even when they happen outside of event handlers, e.g. in a setTimeout or Promise callback. This feature comes out of the box and you don't have to do anything to enable it, and it makes a great argument for upgrading to React 18. Selective Hydration Selective Hydration allows you to take hydration off the main thread by wrapping your components in a Suspense boundary. This way, components can become interactive faster as the browser can do other work on the main thread while the hydration is happening. To fully take advantage of selective hydration, consider the following: - Prioritizing Above-the-Fold Content: Use Suspense boundaries strategically around any parts of your application that may take the server longer to deliver to ensure they don’t block critical content from becoming interactive as soon as possible. - Hydration on Interaction: Implementing hydration upon user interaction for non-critical components can drastically reduce the main thread's workload, enhancing INP. Vercel even has a small case study showing how using selective hydration improved the performance of a Next.js site. Server-Side Rendering (SSR) and Static Site Generation (SSG) in Next.js Not everything has to run client-side. Next.js excels in SSR and SSG capabilities, which can significantly impact INP by delivering content to users faster. Optimizing SSR with techniques like incremental static regeneration (ISR) or leveraging SSG for static pages ensures that users can interact with content faster, improving the perceived performance. Workers Offloading heavy computations to Web Workers can free up the main thread, enhancing the responsiveness of React and Next.js applications. This strategy is especially useful when dealing with third-party scripts. Offloading such scripts in Next.js can be easily done by specifying the "worker" strategy on your Script component. Be aware that this feature is not yet stable and does not work with the app directory, though. If you want to take things one step further, you could use Partytown, which helps you offload any resource-intensive scripts to Web Workers. It comes with a React component that you can use to wrap your third-party scripts and offload them to a Web Worker, and it's compatible with Next.js as well. Hooks and State Management State management in React applications can easily get out of hand, leading to unnecessary re-renders and effectively an increased INP. Sometimes, using a state management library like Redux or MobX can help you consolidate your state and reduce the number of re-renders. However, they are not silver bullets and can also introduce performance issues if not used properly. If you are dealing with a lot of re-renders due to prop changes, make sure you are leveraging memoization. As of now, you may need to work with useMemo and useCallback hooks to memoize your values and functions, respectively. The upcoming React 19’s Forget Compiler, however, will apparently memoize everything under the hood, making these hooks obsolete. Using memoization properly can help you reduce the number of re-renders and improve your INP. To investigate your hook dependencies and re-renders, you can leverage React Developer Tools or use this handy helper hook I found on the internet to trace your re-renders: ` Conclusion Improving INP in React and Next.js is not easy and can require much investigation and fine-tuning. Still, it's worth doing to avoid being penalized by Google in its search results and provide a better experience for your users. Adopting React 18's new features, leveraging SSR and SSG in Next.js, utilizing Web Workers, and optimizing hooks and state management can significantly boost your INP score and deliver a faster application to your users. Remember, INP is just one among many performance metrics emphasizing the need for a comprehensive approach to performance optimization...

Apr 19, 2024

5 mins

Web PerformanceReactNextJSJavaScript

Remix's evolution to a Vite plugin

The Remix / React Router news is a beautiful illustration of software evolution. You start with a clear idea of what you’re building, but it’s impossible to anticipate exactly what it will become. If you haven’t heard the news yet, Ryan Florence announced at React Conf 2024 that Remix will be a Vite plugin for React Router. It’s a sort of surprising announcement but it makes a lot of sense if you’ve been following along as Remix the project has evolved. In this post we’ll recap the evolution of the project and then dig into what this change means for the future of Remix in the Server Components era of React. 🗓️ October 2021 > Remix is open sourced In the beginning, Remix cost money. In October 2021 they received some seed funding and the project was open sourced. Remix was an exciting new framework for server-rendering React websites that included API’s for loading data on the server and submitting data to the server with forms. It started a trend in the front-end framework space that a lot of other popular frameworks have modeled after or taken inspiration from. 🗓️ March 2022 - September 2022 > Remixing React Router At some point they realized that the API’s that they had created for Remix were a more natural fit in React Router. In this post Ryan details the plans to move these Remix API’s into React Router. Several months later, React Router 6.4 is released with the action, loader, and other Remix API’s baked in. > "We've always thought of Remix as "just a compiler and server for React Router" After this release, Remix is now mostly as they described - a compiler and server for React Router. 🗓️ October 2023 - February 2024 > Remix gets Vite support If you’re not familiar with Vite, it’s an extremely popular tool for front-end development that handles things like development servers and code bundling/compiling. A lot of the modern front-end frameworks are built on top of it. Remix announced support for Vite as an alternative option to their existing compiler and server. Since Remix is now mostly “just a compiler and server for React Router” - what’s left of Remix now that Vite can handle those things? 🗓️ May 2024 > Remix is React Router The Remix team releases a post detailing the announcement that Ryan made at React Conf. Looking back through the evolution of the project this doesn’t seem like an out of the blue, crazy announcement. Merging Remix API’s into React Router and then replacing the compiler and server with Vite didn’t leave much for Remix to do as a standalone project. 🐐 React Router - the past, present, and future of React React Router is one of the oldest, and most used packages in the React ecosystem. > Since Remix has always been effectively "React Router: The Framework", we wanted to create a bridge for all these React Router projects to be able to upgrade to Remix. With Remix being baked into React Router and now supporting SPA mode, legacy React Router applications have an easier path for migrating to the next generation of React. https://x.com/ryanflorence/status/1791488550162370709 Remix vs React 19 If you’ve taken a look at React 19 at all, it turns out it now handles a lot of the problems that Remix set out to solve in the first place. Things like Server Components, Server Actions, and Form Actions provide the same sort of programming model that Remix popularized. https://x.com/ryanflorence/status/1791484663883829258 Planned Changes for Remix and React Router Just recently, a post was published giving the exact details of what the changes to Remix and React Router will look like. tl;dr For React Router * React Router v6 to v7 will be a non-breaking upgrade * The Vite plugin from Remix is coming to React Router in v7 * The Vite plugin simply makes existing React Router features more convenient to use, but it isn't required to use React Router v7 * v7 will support both React 18 and React 19 For Remix * What would have been Remix v3 is React Router v7 * Remix v2 to React Router v7 will be a non-breaking upgrade * Remix is coming back better than ever in a future release with an incremental adoption strategy enabled by these changes For Both * React Router v7 comes with new features not in Remix or React Router today: RSC, server actions, static pre-rendering, and enhanced Type Safety across the board The show goes on I love how this project has evolved and I tip my hat to the Remix/React Router team. React Router feels like a cozy blanket in an ecosystem that is going through some major changes which feels uncertain and a little scary at times. The Remix / React Router story is still being written and I’m excited to see where it goes. I’m looking forward to seeing the work they are doing to support React Server Components. A lot of people are pretty excited about RSC’s and there is a lot of room for unique and interesting implementations. Long live React Router 🙌....

Jul 10, 2024

4 mins

ReactViteRemix

How to Create a Custom React Renderer

Creating a Custom React Renderer At the very top of the React documentation, the team defines React's main qualities: - Declarative - Component-Based - Learn Once, Write Anywhere The main focus of the React docs is to demonstrate the first 2 qualities of React: its declarative nature, and how it allows the developer to break logic down into components. The main goal of this article will be to expand upon that third quality of React: "Learn Once, Write Anywhere." Requirements To follow along more easily with this post, you should already know a few things: - React: This post doesn't teach you how to declaratively write React, but instead dives into how React communicates with the DOM. Understanding how to write generic React code would be great foundational knowledge before diving into how it works under the hood. - The DOM: A lot of the interactions between React and the DOM are abstracted away under the 'react-dom' package. Having a good understanding of how to render to the DOM with vanilla JavaScript will be incredibly useful since we will be implementing this functionality ourselves. I've also created a repository based on the create react app starter, and added some nice-to-have features to it including: - TypeScript - ESLint - Prettier - Husky w/ pre-commit linting - Tailwind CSS You can test out your code using a vanilla create-react-app installation, but I enjoy these developer tools, so I wanted to offer a configured setup that uses them. Feel free to clone and use the repo! React DOM I'm sure that every single React developer has run create-react-app at least once. When creating a CRA app, 99% of your time is usually spent expanding the functionality of the App component. Very little time is spent on the piece of logic that actually renders the App component. This line is responsible for taking our React App component, and then mounting all of its components along with event handlers, to the DOM. We usually never need to worry about how React does this. Instead, we focus on declaratively adding functionality to the App components. Rendering to the DOM is abstracted away into this one line. This is similar to working with React Native. We develop Native App Components, but we don't think about *how* those components are rendered to different devices. React Native handles that for us, just like how ReactDOM handles rendering to the DOM for us. The Test Application To test out experimenting with our own custom React renderer, I've created a repository forked off of a create-react-app install, with added dev features like linting, git commit hooks, and TailwindCSS. Before diving into replacing ReactDOM, let's look at what our application can look like at the start. Replacing ReactDOM To replace the react-dom renderer with our own, we'll need to import 2 dependencies: - react-reconciler: This exposes a function that takes a host configuration object, allowing us to customize rendering to whatever format we desire. - @types/react-reconciler: Types for react-reconciler After installing these dependencies, we can replace ReactDOM with our new renderer, and then with the help of TypeScript, stub out the remaining portions of our new Renderer. What does a React renderer look like? The React team exposes their react-reconciler as a function to allow third parties to create custom renderers. This reconciler function takes one argument: a Host Configuration object that's methods provide an interface with which React can render to a host environment. The methods of the host configuration object map out to different methods of the configured host environment, allowing the developer to abstract away the process of rendering and updating the state to the environment. ` For example, here is real code from react-dom, which defines how to append a child in the DOM. In our example exploring this, we'll try and minimally recreate react-dom, so we can render our sample app to the DOM. Host Configuration With a stubbed DOM host configuration, and having replaced ReactDOM with our custom renderer, we are now able to run the CRA dev server without errors. However, nothing has been rendered to the DOM yet. Our host configuration method stubs included console.log's, showing when these methods get called though, so the log has a lot of activity. We can see bits and pieces of our App component in these logs, but since our host configuration did not actually mount anything to the DOM, our screen remains blank. Let's fill out a few of our functions to implement this behavior: - createInstance - createTextInstance - appendInitialChild - appendChild - appendChildToContainer TypeScript does a lot of mental heavy lifting by allowing us to define types and enhancing our development with auto-complete for implementing these host config functions. Types and generic host config signature: ` The createInstance function: ` The createTextInstance function: ` The appendChild function: ` In the end, it was just a few familiar DOM calls until we were able to render our application once again, except this time, with our own renderer! Conclusion With just a few method definitions, we are now able to render to the DOM, but we could have also just as easily issued commands to draw on a canvas when trying to render our components, or we could have rendered differently. By learning React once, you can apply it in a number of scenarios. By separating rendering logic from reconciliation logic, React allows third-party developers to create custom renderers. This allows developers to render whereever they want, be it in the canvas, or even to the console....

Sep 24, 2021

6 mins

React

Introduction to Zod for Data Validation

As web developers, we're often working with data from external sources like APIs we don't control or user inputs submitted to our backends. We can't always rely on this data to take the form we expect, and we can encounter unexpected errors when it deviates from expectations. But with the Zod library, we can define what our data ought to look like and parse the incoming data against those defined schemas. This lets us work with that data confidently, or to quickly throw an error when it isn't correct. Why use Zod? TypeScript is great for letting us define the shape of our data in our code. It helps us write more correct code the first time around by warning us if we are doing something we shouldn't. But TypeScript can't do everything for us. For example, we can define a variable as a string or a number, but we can't say "a string that starts with user_id_ and is 20 characters long" or "an integer between 1 and 5". There are limits to how much TypeScript can narrow down our data for us. Also, TypeScript is a tool for us developers. When we compile our code, our types are not available to the vanilla JavaScript. JavaScript can't validate that the data we actually use in our code matches what we thought we'd get when we wrote our TypeScript types unless you're willing to manually write code to perform those checks. This is where we can reach for a tool like Zod. With Zod, we can write data schemas. These schemas, in the simplest scenarios, look very much like TypeScript types. But we can do more with Zod than we can with TypeScript alone. Zod schemas let us create additional rules for data parsing and validation. A 20-character string that starts with user_id_? It's z.string().startsWith('user_id_').length(20). An integer between 1 and 5 inclusive? It's z.number().int().gte(1).lte(5). Zod's primitives give us many extra functions to be more specific about *exactly* what data we expect. Unlike TypeScript, Zod schemas aren't removed on compilation to JavaScript—we still have access to them! If our app receives some data, we can verify that it matches the expected shape by passing it to your Zod schema's parse function. You'll either get back your data in exactly the shape you defined in your schema, or Zod will give you an error to tell you what was wrong. Zod schemas aren't a replacement for TypeScript; rather, they are an excellent complement. Once we've defined our Zod schema, it's simple to derive a TypeScript type from it and to use that type as we normally would. But when we really need to be sure our data conforms to the schema, we can always parse the data with our schema for that extra confidence. Defining Data Schemas Zod schemas are the variables that define our expectations for the shape of our data, validate those expectations, and transform the data if necessary to match our desired shape. It's easy to start with simple schemas, and to add complexity as required. Zod provides different functions that represent data structures and related validation options, which can be combined to create larger schemas. In many cases, you'll probably be building a schema for a data object with properties of some primitive type. For example, here's a schema that would validate a JavaScript object representing an order for a pizza: ` Zod provides a number of primitives for defining schemas that line up with JavaScript primitives: string, number, bigint, boolean, date, symbol, undefined, and null. It also includes primitives void, any, unknown, and never for additional typing information. In addition to basic primitives, Zod can define object, array, and other native data structure schemas, as well as schemas for data structures not natively part of JavaScript like tuple and enum. The documentation contains considerable detail on the available data structures and how to use them. Parsing and Validating Data with Schemas With Zod schemas, you're not only telling your program what data should look like; you're also creating the tools to easily verify that the incoming data matches the schema definitions. This is where Zod really shines, as it greatly simplifies the process of validating data like user inputs or third party API responses. Let's say you're writing a website form to register new users. At a minimum, you'll need to make sure the new user's email address is a valid email address. For a password, we'll ask for something at least 8 characters long and including one letter, one number, and one special character. (Yes, this is not really the best way to write strong passwords; but for the sake of showing off how Zod works, we're going with it.) We'll also ask the user to confirm their password by typing it twice. First, let's create a Zod schema to model these inputs: ` So far, this schema is pretty basic. It's only making sure that whatever the user types as an email is an email, and it's checking that the password is at least 8 characters long. But it is *not* checking if password and confirmPassword match, nor checking for the complexity requirements. Let's enhance our schema to fix that! ` By adding refine with a custom validation function, we have been able to verify that the passwords match. If they don't, parsing will give us an error to let us know that the data was invalid. We can also chain refine functions to add checks for our password complexity rules: ` Here we've chained multiple refine functions. You could alternatively use superRefine, which gives you even more fine grained control. Now that we've built out our schema and added refinements for extra validation, we can parse some user inputs. Let's see two test cases: one that's bound to fail, and one that will succeed. ` There are two main ways we can use our schema to validate our data: parse and safeParse. The main difference is that parse will throw an error if validation fails, while safeParse will return an object with a success property of either true or false, and either a data property with your parsed data or an error property with the details of a ZodError explaining why the parsing failed. In the case of our example data, userInput2 will parse just fine and return the data for you to use. But userInput1 will create a ZodError listing all of the ways it has failed validation. ` ` We can use these error messages to communicate to the user how they need to fix their form inputs if validation fails. Each error in the list describes the validation failure and gives us a human readable message to go with it. You'll notice that the validation errors for checking for a valid email and for checking password length have a lot of details, but we've got three items at the end of the error list that don't really tell us anything useful: just a custom error of Invalid input. The first is from our refine checking if the passwords match, and the second two are from our refine functions checking for password complexity (numbers and special characters). Let's modify our refine functions so that these errors are useful! We'll add our own error parameters to customize the message we get back and the path to the data that failed validation. ` Now, our error messages from failures in refine are informative! You can figure out which form fields aren't validating from the path, and then display the messages next to form fields to let the user know how to remedy the error. ` By giving our refine checks a custom path and message, we can make better use of the returned errors. In this case, we can highlight specific problem form fields for the user and give them the message about what is wrong. Integrating with TypeScript Integrating Zod with TypeScript is very easy. Using z.infer<typeof YourSchema> will allow you to avoid writing extra TypeScript types that merely reflect the intent of your Zod schemas. You can create a type from any Zod schema like so: ` Using a TypeScript type derived from a Zod schema does *not* give you any extra level of data validation at the type level beyond what TypeScript is capable of. If you create a type from z.string.min(3).max(20), the TypeScript type will still just be string. And when compiled to JavaScript, even that will be gone! That's why you still need to use parse/safeParse on incoming data to validate it before proceeding as if it really does match your requirements. A common pattern with inferring types from Zod schemas is to use the same name for both. Because the schema is a variable, there's no name conflict if the type uses the same name. However, I find that this can lead to confusing situations when trying to import one or the other—my personal preference is to name the Zod schema with Schema at the end to make it clear which is which. Conclusion Zod is an excellent tool for easily and confidently asserting that the data you're working with is exactly the sort of data you were expecting. It gives us the ability to assert at runtime that we've got what we wanted, and allows us to then craft strategies to handle what happens if that data is wrong. Combined with the ability to infer TypeScript types from Zod schemas, it lets us write and run more reliable code with greater confidence....

Nov 15, 2024

7 mins

JavaScriptZod

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Getting Started with React and TypeScript

Getting Started with React and TypeScript

Prerequisites

Create React App

Folder Structure

Hello, World - With TypeScript and React

Adding a bit of TypeScript

Benefits of TypeScript

Conclusion

Matthew Pagan

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