Switch to ESM Jest config in docs (#42144)
Thanks again for Next.js 13! Finding a bunch of new ways to improve things 🙌
Just a quick PR to switch the Jest configuration file with `next/jest` to ESM to eliminate another instance of CommonJS.
ESM requires a `.js` extension on the import.
An alternative would be to switch to a TypeScript config file (`jest.config.ts`) which would (I am guessing) not require this file extension (but still allow switching to an ESM-style `import` syntax).
New version in the diff:
```js
// jest.config.mjs
import nextJest from 'next/jest.js'
const createJestConfig = nextJest({
// Provide the path to your Next.js app to load next.config.js and .env files in your test environment
dir: './',
})
// Add any custom config to be passed to Jest
/** @type {import('jest').Config} */
const config = {
// Add more setup options before each test is run
// setupFilesAfterEnv: ['<rootDir>/jest.setup.js'],
// if using TypeScript with a baseUrl set to the root directory then you need the below for alias' to work
moduleDirectories: ['node_modules', '<rootDir>/'],
testEnvironment: 'jest-environment-jsdom',
}
// createJestConfig is exported this way to ensure that next/jest can load the Next.js config which is async
export default createJestConfig(config)
```
## Bug
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have a helpful link attached, see `contributing.md`
## Feature
- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [x] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have a helpful link attached, see `contributing.md`
## Documentation / Examples
- [ ] Make sure the linting passes by running `pnpm build && pnpm lint`
- [ ] The "examples guidelines" are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)
