React TypeScript Example (2022)

This repo contains a React app written in TypeScript using vite as a bundler and build tool. Its purpose is to document and demonstrate the JS Dev team's opinions, best practices, preferred libraries, testing methodology, and application architecture.

Note: This repo represents a snapshot in time. The frontend development landscape is notorious for changing rapidly. It is not expected for this project to be maintained and adapted over time, though contributions are welcome.

Setup

$ bin/setup

Run the app

$ bin/server

Styling

This app uses emotion with the styled variation. This variation is preferred (over the css prop) because it allows for highly expressive and tidy jsx (using appropriately named styled components with descriptive names that indicate their intended purpose).

Within the styled API, this app uses the CSS object notation which looks like:

const Button = styled('button')(({ theme }) => ({
  background: theme.colors.background,
}))

This approach has several benefits:

• better support for intellisense over css string template literals
• more concise when referencing props such as the theme

Note(10/12/2022): For some unknown reason using the latest versions of @emotion/react and @emotion/styled (11.10.4) breaks the tests in some strange and undebuggable way. The ThemeProvider does not seem to properly provide the theme to styled components.

For this reason, we explicitly depend on 11.9.3 as a workaround until the issue is resolved.

Testing

Running Unit Tests

To run the test suite once, immediately, use:

$ bin/test

This also supports optionally passing a test file name that will be fuzzy matched against all the specs that vitest knows about, e.g.:

$ bin/test counter

Interactively Running Tests (watch mode):

To run tests in watch mode:

$ npm run test:watch

If you want to open the browser UI:

$ npm run test:watch -- --ui

Running Test Coverage

Test coverage is provided by vitest using the istanbul provider. Reporters are configured for html-spa (handy for local browsing), text (cli output), and clover (XML report used in CI).

$ bin/cov

Reports are generated in the coverage folder.

Ignoring lines for coverage

Istanbul supports special comments for ignoring certain lines for the purposes of calculating test coverage. But because of this issue the comments you add may not have any effect on the coverage due to esbuild removing the comments during compilation. There is a PR to Istanbul to allow for "legal comments" (/*! istanbul ignore next */) which shouldn't get stripped but for the time being we use /* istanbul ignore next -- @preserve */.