Welcome to building a web application using React!

The target audience of this series of posts are people who have some prior experience using React, and ideally some experience using a state management library such as Redux or MobX. The main aim is to show an opinionated way that a non-toy application can be built.

During the series, we're going to building a site that will let users create and vote on polls. The site will call to an existing API server hosted at which will mean we don't have to worry about setting it up ourselves.

Before we start

Before we can start the real work of building the site, we need to make sure we have the appropriate tools to do the job.

Install or update to the latest stable version of Node

Direct downloads are available here

Make sure your npm directory is added to your PATH so it's accessible via command line. You can test if it's working using to see the NPM version that's installed.

Update to the latest NPM:     

npm i -g npm@latest

Make sure you have an IDE or text editor installed and up to date

If in doubt, Visual Studio Code is a great option.


React DevTools Browser Extension for Chrome or Firefox. The React DevTools should "just work" when you're developing a React application. It has useful tabs for see the current props and state of components, and finds what's actually rendered. It also has a performance profiler to help track down issues if anything happens to run slowly.

Create the new project

The first step is to create the new React project. To do this we'll be using create-react-app, which is an opinionated way to structure a React application development environment.

It's likely that many readers will have used create-react-app before, but we'll run through the process for completeness.

While being opinionated means that possible options may not be available, it also means that we don't have to deal with the details of the WebPack/Babel build pipeline. Additionally, the maintainers of this project work hard to make updating projects to new React versions as easy as possible, which is very valuable for projects that are going to be supported over the medium to long term.

Run the commands below in your favourite terminal. Our new project will be called "repoll".

Note we are explicitly saying to use npm - if you'd prefer to use yarn and have it installed, you can remove that option. We are also going to use TypeScript, because why wouldn't you? 😉

npx create-react-app@latest repoll --use-npm --template typescript

The React docs give a brief overview of the files that are generated.

Now check that it works by changing the current directory to the repoll folder and using npm start, which should display the new-generated web app in your default browser. You can also run the generated test using npm test.

The available npm commands and what they do is described in the generated file.

Note that create-react-app has also initialised the project as a git repository with a single commit containing the generated files.

Git Attributes

Add a .gitattributes file to the root of the project with the following contents, so that line endings are treated the Unix way. Even on Windows any text editor/IDE should be fine with this.

* text=auto eol=lf
*.{cmd,[cC][mM][dD]} text eol=crlf
*.{bat,[bB][aA][tT]} text eol=crlf

📔 This code is taken from this VSCode documentation about sharing repos between Windows and Linux.

You can run git add --renormalize . to apply "renormalisation" to the already committed files. If any changes are staged they can then be committed to get everything consistent.

Tweaking the generated app

The generated application does many things automatically for you, and generally has sensible defaults, but there are a few changes that I suggest are a good idea.

Stop auto-opening a browser window

The default behaviour of create-react-app is to open a browser whenever npm start is run. This is great when you've not used create-react-app before, but personally I find it gets annoying as I'm stopping and starting the react dev server often and don't need a new browser tab each time.

To change this, add a new .env file to the root (/repoll) directory with the following contents:


The .env file sets environment variables to default values. See the docs for extensive details about how to set environment variables and how to use them within the app.

Update dependencies

The generated project may not use the latest versions of all of its dependencies. But as we're just starting out, now's the time to use the latest and greatest!

Run npm outdated to see what newer versions are available.

To update everything to the latest versions, run the following:

npx npm-check-updates -u
npm install

📔 npm-check-updates is an independent package - it also has many additional options if the command above is not suitable.


The default project uses regular css for styling. We're going to change this to use CSS Modules with SASS. For this tutorial, we'll be going with the following:

◾ CSS Modules over global styles

◾ Preferring the use of React Components to apply styles

◾ SASS rather than plain CSS

◾ CSS Properties/Variables over SASS variables for colours


◾  CSS Modules automatically makes unique style class names, and allows styles to be imported as an object which may improve editor intellisense.

◾  Using components (eg a <Button> rather than <button className="button">) means that global style names do not need to be remembered, and modifications (such as having a "primary" or "alternate" button) can be added as optional props, and discovered using intellisense.

◾  Using SASS is a simple compile-time addition to the project. While many of SASS's features are not needed, some are still useful to use from time to time, such as to avoid repetition.

◾  CSS Properties can have their values declared in your typescript code, rather than in your SASS, and are scoped to the element that they're applied to and its children. This makes it really simple to change their values at runtime to apply things like theming. It does mean that some SASS features (like darken) cannot be used however (but there are usually suitable alternatives).

CSS Modules are automatically supported, but for Sass we need to install a library to help. If you follow the standard create-react-app docs, they will suggest installing node-sass. However, currently node-sass does not support the newer features of SASS, such as @use. Instead, create-react-app now has support for dart-sass and so we can use a js implmentation of it.

📔 There are some trade-offs involved in this choice of which sass library to use: sass is more up-to-date with features, and is js-only with fewer dependencies, while node-sass uses a C++ implmentation, so it is faster to compile.

We want to use the latest SASS features like @use, so run the following:

npm i sass

📔 You may also find that your editor has a CSS Modules extension. For VSCode, there's the CSS Modules extension that can help with intellisense and go-to-definition.

Now we'll update some of the existing pages to use CSS Modules and SASS

◾ Change the main index.css file to use Sass:

◾ Rename src/index.css to src/index.scss. Having this one non-module css file gives a convenient location for apply style resets and any custom global styles (of which there should not be many as we'll be using React components!)
◾ Change src/index.tsx to update the import of the style file to match the new name

◾ Change the App.css to use Css Modules

◾ Rename src/App.css to src/App.module.scss
◾ Update the styles within the file

◾ change the App class to root (an optional change, but a useful convention for the style that will be applied to the root element)
◾ remove the App- prefix from the remaining classes (as Modules automatically unique-ifies the names for us)

◾ Update the existing css import in src/App.tsx to be:

import styles from './App.module.scss';

When using modules, styles are imported and used directly, rather than specifying a "magic string". So update the className attributes in the App.tsx file like the following:

className="App" -> className={styles.root}
className="App-header" -> className={styles.header}
className="App-logo" -> className={styles.logo}
className="App-link" -> className={}

If you installed a Css Modules editor extension, hopefully you had some intellisense on the styles object.

Note that when a class name is a single word, you can use dot-notation from the styles instance. If you have a name like foo-bar, you need to use an indexer styles['foo-bar'].

create-react-app also contains PostCSS Normalize, that can be opted-into if desired by adding @import-normalize; to the top of index.scss.

📔 Note that in VSCode, you may get a warning about having an "unknown at rule" - this can be ignored, or turned off in VSCode's SCSS settings.


the main index.css file to use Sass:

Rename src/index.css to src/index.scss. Having this one
non-module css file gives a convenient location for apply style resets
and any custom global styles (of which there should not be many as we'll
be using React components!)
Change src/index.tsx to update the import of the style file
to match the new name


• Change the main index.css file to use Sass:
o Rename src/index.css to src/index.scss. Having this one non-module css file gives a convenient location for apply style resets and any custom global styles (of which there should not be many as we'll be using React components!)
o Change src/index.tsx to update the import of the style file to match the new name