In the previous guide, we built a streaming chat interface using the raw OpenAI API. It worked, but required a fair bit of manual work: decoding text streams, managing message state, and wiring everything together from scratch. That approach is great for learning, but in real-world projects, you often want something more ergonomic, robust, and…

In this tutorial, you'll build a simple AI chat app using React.js on Next.js and the OpenAI API. You'll learn how to set up an API route to send prompts to OpenAI and build a frontend that displays the conversation in real time. By the end, you'll have a working full-stack AI application that you can expand upon. In addition, we will also learn…

Since it became possible to create full-stack applications with React, the question of authorization has been a recurring topic. In this extensive guide, I want to explore how authorization can be implemented in Next.js when using React Server Components and Server Actions in Next's App Router. While this guide follows the event of the recent…

React has been around for quite some time, and over the years, an extensive—yet sometimes overwhelming—ecosystem of libraries has grown around it. Developers transitioning from other languages or frameworks often struggle to navigate all the libraries needed to build web applications with React. At its core, React allows developers to build…

Every year, I want to give you a brief overview of how to start a new React project. I'll reflect on the advantages and disadvantages, the skill level needed as a developer, and the features each starter project offers to you as a React developer. By the end, you'll know about three solutions for different requirements. React with Vite Vite is…

After using the MacBook Pro 2015 for several years, I upgraded to a MacBook Pro 2021 a while ago. The years with my previous Mac were fantastic, and now, with the newer MacBook Pro, I continue to work efficiently on my freelance web development projects. My goal is to keep this MacOS setup for web development up-to-date for you. Here comes…

In the previous guide, we built a streaming chat interface using the raw OpenAI API. It worked, but required a fair bit of manual work: decoding text streams, managing message state, and wiring everything together from scratch. That approach is great for learning, but in real-world projects, you often want something more ergonomic, robust, and…

In this tutorial, you'll build a simple AI chat app using React.js on Next.js and the OpenAI API. You'll learn how to set up an API route to send prompts to OpenAI and build a frontend that displays the conversation in real time. By the end, you'll have a working full-stack AI application that you can expand upon. In addition, we will also learn…

Every year I discuss the most important trends in the world of React. In this article, we will explore the React trends in 2025 that you should be aware of. Whether you are a beginner or an experienced developer, these trends will help you stay up-to-date with the latest developments in the React ecosystem. React Server Components We've come a long…

I explored Authentication in Next.js 15 using Next's App Router, React Server Components (RSC), and Server Actions. This comprehensive tutorial covers hand rolling your own authentication for sign up, sign in, sign out, and protected routes. If you want to go beyond this with the implementation of password change, password reset, forgot password…

State in web applications can have many forms. It can be local component state, global application state, browser state or shareable URL state . The latter is a special form of state that is stored in the URL which then can be shared with others or saved for later use. Once this URL is visited again, the application's state is restored from the…

I have been working with React Server Components and Server Actions in Next.js for the last 6 months. While I am excited about Server Components and their ability to execute code on the server, I am not convinced (yet) by the story of data fetching in Client Components (without Server Actions). Since I have seen the question ("Can I fetch data with…

In this tutorial, you will learn how to build a simple interactive CLI app with Node.js and TypeScript. The app will create a chat interface that reads user input and responds interactively. Let's get started! To run the app, execute the following command in your terminal: This will start the CLI app and display the welcome message. You can now…

Setting up a TypeScript project with Node.js may seem like a hassle at first, but with the right steps, you'll have everything running smoothly in no time. Whether you're building a small script or a full-fledged application, this guide will walk you through the entire process. We'll start from scratch, configure TypeScript, and set up a simple…

tRPC allows developers to create fully type safe APIs with TypeScript in full-stack applications. While the server application produces a type safe router with type safe functions (e.g. CRUD operations: create user, get user by identifier, get all users), the client application can call these functions directly on the inferred type safe router…

Let's learn about using LangChain in JavaScript for streaming structured output responses from the backend to the frontend while building a chatbot application that interacts with the OpenAI API to generate responses to user prompts. In this tutorial we will be using Next.js (with React.js) for the frontend (UI) and backend (API). The finished…

Let's learn about using LangChain in JavaScript for structured output responses from the backend to the frontend while building a chatbot application that interacts with the OpenAI API to generate responses to user prompts. In this tutorial we will be using Next.js (with React.js) for the frontend (UI) and backend (API). The finished project can…

Let's learn about using LangChain in JavaScript for streaming responses from the backend to the frontend while building a chatbot application that interacts with the OpenAI API to generate responses to user prompts. In this tutorial we will be using Next.js (with React.js) for the frontend (UI) and backend (API). The finished project can be found…

Setting up a TypeScript project with Node.js may seem like a hassle at first, but with the right steps, you'll have everything running smoothly in no time. Whether you're building a small script or a full-fledged application, this guide will walk you through the entire process. We'll start from scratch, configure TypeScript, and set up a simple…

This is a comprehensive tutorial on Monorepos in JavaScript and TypeScript -- which is using state of the art tools for monorepo architectures in projects. You will learn about the following topics from this tutorial. I've become passionate about monorepos, as they've transformed how I approach my work as a freelance developer and contributor to…

Authentication is an important topic of any application. It's the gatekeeper that ensures only the right people can access the right resources. But how do you roll your own authentication in JavaScript & TypeScript ? In this tutorial, we'll explore how to build a session-based authentication system where a database is used to store users and their…

Authentication is an important topic of any application. It's the gatekeeper that ensures only the right people can access the right resources. But how do you roll your own authentication in JavaScript & TypeScript ? In this tutorial, we'll explore how to build a session-based authentication system where a database is used to store users and their…

Rounding errors are a common issue in JavaScript and other programming languages when working with floating-point numbers. You might have encountered the problem when adding two decimal numbers like 0.1 + 0.2 and expecting the result to be 0.3 . However, the result is not 0.3 but 0.30000000000000004 . In a financial application you do not…

The JavaScript and web development community evolves quickly and new frameworks come and go. There are many people learning React, Angular, Vue or Svelte nowadays. They are not only computer science graduates, like it used to be in the past, but also self-taught programmers coming from bootcamps and other backgrounds. I find it amazing that the…

A quick migration guide to Vite from Create React App, because (apart from Next.js) Vite is the natural successor of CRA for creating a modern React application as SPA . First, install Vite and all React related libraries (here: Vite's React Plugin) as development dependencies: Second, uninstall create-react-app's dependency: Third, adjust your…

A quick tutorial for setting up ESLint in Vite. We will make the case for using linting (as general programming concept) with ESLint (JavaScript tool for linting) for the following Vite + React project, because it catches errors early. However, you can do it for any other Vite template. We will start with a basic App component which has an unused…

A brief walkthrough on how to set up React Testing Library in Vitest when using Vite. The tutorial assumes that you have already created a React project with Vite either in JavaScript or TypeScript. Next, install Vitest on the command line: Then in your package.json file, add another script which will run the tests eventually: Create a test…

A question that comes to mind for every web development beginner: How to set up my web development environment as a web developer? The following guides have you covered, because they will teach you how to set up a minimal web development environment for MacOS or Windows. Even though you will start out with HTML, CSS, and JavaScript as a web…

In this article, you will find a step by step guide on how to install React on MacOS. It follows the philosophy of having one IDE to manage most of your web development tasks. That's how you can focus on your task at hand as a developer. However, if you like to compose your development environment with lightweight tools rather than with an full…

In this article, you will find a step by step guide on how to install React on Windows. There are plenty of articles out there on how to setup your web development environment on MacOS, but very few on how to setup it on Windows. Especially when people want to enter the world of React.js in Windows, there is a missing starting point. I wanted to…

A React Router tutorial which teaches you how to use Descendant Routes with React Router 7 . The code for this React Router v7 tutorial can be found over here . The previous tutorial of Nested Routes has shown you how to replace a part of a component depending on the URL with the help of the Outlet component. This way, in the last example, we…

A React Router tutorial which teaches you how to use Nested Routes with React Router 7 . The code for this React Router v7 tutorial can be found over here . Nested Routes are a powerful feature. While most people think React Router only routes a user from page to page, it also allows one to exchange specific fragments of the view based on the…

A React Router tutorial which teaches you how to use Lazy Loading with React Router 7 . The code for this React Router v7 tutorial can be found over here . Lazy Loading on route level with React Router is a powerful feature. Usually a client-side rendered React applications comes as one bundle from a web server. However, when enabling lazy…

As a freelance React developer, I work with a lot of clients on their React projects these days. Every time I get a request in my inbox, I usually reply with the same email template which I call the freelance checklist for React developers . If you are going to sign up for my Newsletter, you will get two email templates -- one from the perspective…

When using React's useState Hook in TypeScript, the method usually infers the implicit type for the returned state from the provided argument automatically. In the following example, React's useState Hook in a function component knows that it deals with a number type. Hence the returned state (here: count ) has the type number in addition to…

A brief summary of how to use React's useRef Hook for using a ref with TypeScript. First, a ref in React is mainly used to assign a HTML element to it. The assigned HTML element gives us imperative read and write operations on it which allows us to programmatically call functions. Take the following example for focusing an input element: When using…

React introduced Hooks quite a while ago. With their release, Hooks gave function components the ability to use state and side-effects with built-in Hooks such as React's useState Hook and React's useEffect Hook . There are only a handful built-in Hooks (e.g. useReducer , useCallback , useMemo , useContext ) provided by React though…

A beginner-friendly React tutorial that walks you through creating a dropdown component by example. In this guide, you'll learn step by step how to build a dropdown in React. While HTML offers a built-in select element for similar functionality, React doesn't have such native primitives for dropdown components. First, we need a HTML button element…

Material UI for React, also called MUI, does not come with a native CrossFade component for transitioning with a cross fade animation between two or more components. Here I want to share the cross fade component that I have used for several of my freelance projects when using Material UI: And the usage of this CrossFade component appears as follows…

Material UI for React, also called MUI, does not come with a native nested Dropdown menu. Here I want to share the nested dropdown component that I have used for several of my freelance projects when using Material UI. Before you can use it, you have to check out my implementation for a dropdown with Material UI (MUI) in React: In the Dropdown…

In this article, you will find a step by step guide on how to install React on Windows. There are plenty of articles out there on how to setup your web development environment on MacOS, but very few on how to setup it on Windows. Especially when people want to enter the world of React.js in Windows, there is a missing starting point. I wanted to…

The default setup for my JavaScript projects: Prettier + ESLint. Whereas Prettier is used to autoformat my code to enforce an opinionated code format, ESLint makes sure to keep my code style in a good shape. In this brief setup guide, I want to show you how to combine Prettier with ESLint without wasting any tear. If you haven't set up Prettier yet…

A brief step by step tutorial on how to install and use ESLint in VS Code (Visual Studio Code) . ESLint supports you and teams to follow a common code style in your project. It can be used in VS Code by installing it from the VS Code Marketplace. Once you have integrated it in VS Code, you can configure ESLint to enforce a code style in your…

Recently I have read Give and Take: A revolutionary approach to Success by Adam Grant. It is an inspiring book and I found myself taking too many notes while reading it. Now I want to summarize my learnings, to internalize them, but also to give others access to it. In his book, Adam Grant dives deep into the spectrum of altruistic to selfish…

"A state of flow can be achieved by deep work". The subjects flow and deep work are covered in the books Deep Work by Cal Newport and Flow by Mihaly Csikszentmihalyi. I read both books, personally I can say that they are outstanding, and they can be well combined when it comes to satisfaction in a person's life. The following article summarizes my…

As a software engineer you will come to a point where writing matters. Perhaps you want to leave your fellow developers a note, you have to write an e-mail to a customer or you have to sum up the recent meeting notes. In my case, it went even further because I have my own website where I write about software development and where I started to…

When using React Router in React, one can use the Navigate component to navigate a user away from a page in case of a certain condition. For example, the following example does not render a list if there is no data, but redirects a user to the home page instead: In this case the redirect is well placed. However, if there is much logic happening…

In a modern React world, everyone uses function components with React Hooks . However, the concept of higher-order components (HOC) is still applicable in a modern React world, because they can be used for class components and function components. Therefore they are the perfect bridge for using reusable abstractions among legacy and modern…

In this tutorial, I want to show you how to use React Table Library to create a Tree Table or Tree List . In the previous example, you installed React Table Library to create a table component. Now, we will enable users to expand and collapse rows in a React Tree View . First, import the useTree hook: And second, initialize it with the table…

In this tutorial, I want to show you how to use React Table Library with its useRowSelect plugin to implement a select feature. In the previous example, you installed React Table Library to create a table component. Now, we will enable users to select a row in the table by either clicking the row or clicking a checkbox. First, import the…

In this tutorial, I want to show you how to use React Table Library with double click on a row. In the previous example, you installed React Table Library to create a table component. A single click on a row is enabled in the following way: By contrast, a double click on a row can be achieved in this way: Keep in mind that enabling double click…

If you happen to have a custom Webpack setup, you may be wondering how to set up React Router with Webpack. Let's say we have the following minimal React application using React Router: If you open your React application and navigate between both paths, everything should be fine. However, if you navigate via the browser's URL bar to /about, you…

The previous tutorials have shown you how to set up a basic web application with Webpack 5. So far, Webpack is only used to bundle all your JavaScript files, to transpile new JavaScript features via Babel, and to serve your bundle in development mode via Webpack's Development Server. Basically that's everything that's needed to get started with…

In this tutorial, you will learn how to set up Webpack to use images as assets for your application. Essentially, there is not much in Webpack to include your desired images for your web application. First, put your image files into one folder of your projects application. For instance, your src/ folder may have a folder assets/ which has a…

In this tutorial, you will learn how to set up a local font with Webpack. We will use Open Sans, but you can decide to use any other web font as well. If you have your font files already at your disposal, don't bother about downloading them again. For our case, we will download the font to our local setup from Google Webfonts . Therefore, follow…

The previous tutorials have shown you how to set up a basic web application with Webpack 5. So far, Webpack is only used to bundle all your JavaScript files, to transpile new JavaScript features via Babel, and to serve your bundle in development mode via Webpack's Development Server. Basically that's everything that's needed to get started with…

In this tutorial, you will learn how to set up Webpack to use images as assets for your application. Essentially, there is not much in Webpack to include your desired images for your web application. First, put your image files into one folder of your projects application. For instance, your src/ folder may have a folder assets/ which has a…

In this tutorial, you will learn how to set up a local font with Webpack. We will use Open Sans, but you can decide to use any other web font as well. If you have your font files already at your disposal, don't bother about downloading them again. For our case, we will download the font to our local setup from Google Webfonts . Therefore, follow…

In this brief walkthrough, we will use Babel Module Resolver to convert relative paths to aliases for your entire JavaScript application. You can install it via the command line: And use it in your .babelrc file to create your first module alias: In this case, we are giving all our Icons an alias path. Imagine you would have another src…

In this tutorial I want to walk you through setting up ESLint for React. You should go through the previous tutorials in order to learn about the basic setup for Webpack and ESLint though. It will also tell you about all the benefits that come with the code style improvements which ESLint is giving your projects. Webpack and Babel for React ESLint…

For all my React Native tutorials, I intend to use Expo as baseline, because it just makes things so much easier when developing an app with React Native. If you want to follow my tutorials about React Native, you should get this setup right. React Native with Expo Expo is a powerful environment for React Native which helps you from creation to…

Oak, the successor of Koa (which is the spiritual successor of Express in Node.js), is the most popular choice when it comes to building web applications with Deno. However, when saying web applications with Deno, it's often not for anything visible in the browser (excluding server-side rendering of a frontend application). Instead, Oak, a web…

Environment variables are great for hiding sensitive information about your Deno application. This can be API keys, passwords, or other data which shouldn't be visible to others. That's why there exists the .env file, which you would have to create, to hide sensitive information. We will create this file and pass some sensitive information to it…

Deno is a new runtime for JavaScript and TypeScript. If this doesn't tell you much and you don't know what to expect, then take this statement as secondary introduction: Ryan Dahl, inventor of Node.js, released Deno in 2020 as answer to improve Node.js. However, Deno isn't Node.js, but a complete new runtime for JavaScript, but also TypeScript…

GraphQL resolvers are used to resolve GraphQL queries to actual data. In this GraphQL tutorial, you will learn how to set up a GraphQL middleware for these resolvers for dealing with authorization and permissions. The following code snippet shows a GraphQL resolver with arguments that creates a new entity in a database. In this scenario, a user…

Every time I used Firebase, I ran into the problem of how to test Firebase's database and authentication. Since I am using Jest as my default testing environment, I figured everything I needed already comes with Jest. In this tutorial, you will learn how to mock Firebase's features. We will use Firebase Admin SDK for the Firebase setup, however…

So far, it was fine to rely only on React's local state and React's Context API. This tutorial dives into using MobX on top of React and Firebase for the state management. We'll exchange React's local state (e.g. users on admin page, messages on home page) and React's context (e.g. session management for authenticated user) with MobX. It will how…

A collection of all the Docker commands I am using on a regular basis for developing applications with Docker. Docker Machine List all Docker engines: Create a Docker engine: Set environment variables for Docker engine: Start a Docker engine: Stop a Docker engine: Retrieve IP address for running Docker engine: Docker Images List Docker images…

Just recently I had to use Docker for my React web application development. Here I want to give you a brief walkthrough on how to achieve it. First of all, we need a React application. Either create a React app yourself, or follow this minimal React with Webpack setup guide . The React + Webpack application can be found on GitHub too. Note: If…

Just recently I had to use Docker for my create-react-app web application development. Here I want to give you a brief walkthrough on how to achieve it. First of all, we need a React application. Either create a React app with create-react-app yourself, or follow this React MacOS setup guide or this React Windows setup guide . Note: If you are…

React components connected to Redux can turn out pretty complex. Thus most people think that testing these complex components can turn out very complex as well. But it shouldn't be complex at all, if you take full control of the Redux store in your integration/unit test for the React component. I will use only Jest in this brief testing tutorial…

The following implementation shows you how to integrate Redux Persist into Next.js with a quick example. First, the installation of the library on the command line: Second, rather than having a straightforward function which creates our Redux store, we distinguish between server-side and client-side Redux store. In the case of the client-side…

The previous tutorial series covered a lot of ground for Firebase in React. So far, it was fine to rely only on React's local state and React's Context API. This tutorial dives into using Redux on top of React and Firebase for state management. You will exchange React's local state (e.g. users on admin page, messages on home page) and React's…

If you are using Snapshot Tests with Jest for your components, there are a few pitfalls you have to be aware of. Two of them are very likely to apply to your written tests as well: 1) The output of snapshot tests becomes most often too large, if the actual snapshot test renders a component with lots of child components. This holds two problems in…

Jest got introduced by Facebook for testing JavaScript and especially React applications. It's one of the most popular ways to test React components nowadays. Since it comes with its own test runner, you can simply call Jest from the command line to run all your tests. All your tests are defined as test suites (e.g. describe -block) and test…

In this React testing tutorial, we will introduce Enzyme in our Jest testing environment. Jest is commonly used as test runner -- to be able to run your test suites and test cases from the command line with optional configuration -- but also to make assertions in your test cases. In contrast, Enzyme can be used within Jest to render components, to…

This tutorial teaches you how to build your first Web Components and how to use them in your applications. Before we get started, let's take a moment to learn more about Web Components in general: In recent years, Web Components, also called Custom Elements , have become a standard API for several browsers which allow developers to implement…

MobX is used for state management in modern applications. Often it is applied in a React.js application, but it is not necessarily bound to React. In addition, it is a valuable alternative to Redux as state management solution. If you are using create-react-app as your application boilerplate, you most likely run into the questions of how to…

I am excited to launch my course The Road to Redux . I worked on the course for the last 6 months and squeezed every of my free minutes during a workweek, weekends and holidays into it. For instance, when writing the book, I woke up two hours earlier before my 9 to 5 job to write ~750 qualitative words a day. It continued by building a platform…

I used Redux excessively the last years, but spent the recent time with MobX as state management alternative. It seems that Redux alternatives evolve naturally into confusion in the community. People are uncertain which solution to pick. The issue isn't necessarily Redux vs MobX . Whenever there exists an alternative, people are curious what…

Before we start to build full-fledged GraphQL applications, on the client- and server-side, let's explore GraphQL with the tools we have installed in the previous sections. You can either use GraphiQL or the GitHub's GraphQL Explorer. In the following, you will learn about GraphQL's fundamentals by executing your first GraphQL queries, mutations…

Apollo is an entire ecosystem built by developers as an infrastructure for GraphQL applications. You can use it on the client-side for a GraphQL client application, or server-side for a GraphQL server application. At the time of writing this tutorial, Apollo offers the richest and most popular ecosystem around GraphQL in JavaScript. There are other…

In a previous application, you have learned how to mock a GraphQL server in different ways when having Apollo Client as GraphQL client in your React application. The following application shows you how you can take this knowledge to the next level for writing tests for your Apollo Client queries and mutations. So far, the Apollo Client instance can…

I did a lot of Angular 1.x back in the days until I started to use React. I can say that I used both solutions extensively. But there were and are several reasons why I moved to React. These reasons were not clear from the beginning, but retrospectively I think I can summarize these very well. In the following I want to give you 10 reasons why I…

Components become more important these days. In the future you will get to hear more and more about Web Components, which get available in Angular 2.0 as well, to create different reusable components. While you already weave multiple angular directives into each other, there are only a few articles which describe this reusability with d3 directives…

This article shows how you can achieve Small Multiples with D3 using Angular.js. According to Edward Tufte (1983) Small Multiples are a concept to visualize multiple homogenous visualizations like maps, line graphs or scatterplots. We will use this visualization concept to draw multiple line graphs with D3 on Angular. Here you can find an example…

A couple of my recent articles gave an introduction into a subfield of artificial intelligence by implementing foundational machine learning algorithms in JavaScript (e.g. linear regression with gradient descent , linear regression with normal equation or logistic regression with gradient descent ). These machine learning algorithms were…

A couple of my recent articles gave an introduction to machine learning in JavaScript by solving regression problems with linear regression using gradient descent or normal equation . In a regression problem, an algorithm is trained to predict continuous values . It can be housing prices in a specific area based on a feature set such as…

A recent article gave an introduction to the field of machine learning in JavaScript by predicting housing prices with gradient descent in a univariate regression problem. It used plain mathematical expressions and thus made use of the unvectorized implementation of gradient descent and the cost function. However, the unvectorized approach doesn…

This article shows how you can achieve Small Multiples with D3 using Angular.js. According to Edward Tufte (1983) Small Multiples are a concept to visualize multiple homogenous visualizations like maps, line graphs or scatterplots. We will use this visualization concept to draw multiple line graphs with D3 on Angular. Here you can find an example…

Last year Apple released their new collection of iPhones. One innovation of Apple which caught my eyes is the new health app. The dashboard with its health charts is appealing and well designed. Therefore I had to remake one of its components with D3.js. This is what you are going to achieve. Gist for Source Code Example with Source Code…