Sergio Xalambrí
August 27, 2019

# Next.js File Structure

Overview of the file structure I like to use in Next.js projects

React doesn't have a strong opinions on how to structure your files. Similarly Next.js has a few opinions, create a
`pages` and `static` directory and that's all.

I have worked on a few Next.js based projects, one of them the ZEIT website who are the creators of this tools.

This article is a summary of the folders I like to create when working in a Next.js based application.

    ├── __mocks__
    ├── __tests__
    │   └──  __snapshots__
    ├── components
    │   ├── __snapshots__
    │   ├── {name}.js
    │   └── {name}.test.js
    ├── e2e
    │   ├── helpers
    ├── hooks
    ├── pages
    │   ├── _app.js
    │   └── _document.js
    │   └── _error.js
    ├── static
    └── utils

## __mocks__

In this folder I place the mocks for installed modules I will use in any integration or unit tests. Mocks must have the same name of the imported file, in cases like `next/link` which are nested modules we need to create a `next` folder and put the `link.js` file inside it.

## __tests__

Here are the integration tests, each integration tests should match a page inside the pages directory.

### __tests__/__snapshots__

Any snapshot generated by the integration test will be placed inside this folder. It's automatically generated by Jest when doing a snapshot test.

## components

Here are the React component which could be reused in multiple pages or are complex enough to move them to another file and test them individually.

Each file should have a default export with a single component, inside the file there could be multiple components though. The file name must use kebab-case.

Each component here should have at least an snapshot tests, the test file should be in this same folder with the same file name adding `.test.js` as file extension.

### components/__snapshots__

It's the same as __tests__/__snapshots__ but for the unit test of each component.

## e2e

Here is where the End To End tests are placed. Each file should have the `.test.js` extension to be recognized as a test. Any other file should be ignored by the E2E testing tool (I personally use TestCafe)

### helpers

If a helper function is required for the E2E tests it should be placed here. The file could not end with `.test.js` since it will be considered a test suite.

Those are, ideally tiny, functions used in any E2E test, e.g. a `setCookie` function.

## hooks

Any custom hook created for the application should be placed here, test files are ideal but not required since a hook could be tested by the integration or unit tests of the components which are using them.

Note hooks in this place are intended to be used by multiple components, any custom hook created to be used in a single component should be placed in the component file itself.

## pages

Here are the pages (also known as views) of the application, each file will automatically match a route as described in Next.js documentation.

The `_app.js` is a special file which will be the the main application component.

The `_document.js` is a special file which will only be used Server Side to render the basic HTML of the application.

The `_error.js` is a special file which will be used to customize the Next.js error page.

## static

Any static file required by the application (images, audios, etc.) could be placed here.

This is a normal Next.js folder, nothing special here.

## utils

Here I place any utility function I create for my projects, things you would probably import from `lodash`, `date-fns` or another library like that but created specifically for my project.

## Final Words

This is the file structure I found useful when working with Next.js and that it helped using the framework.

It doesn't mean it's the best one and it could probably be improved or changed in a per project basis. Remember the best file structure is to move files around until it feels right.

Do you use something like this? Do you use something completely different? Let me know at @sergiodxa.