electron/docs/development/coding-style.md

# Coding Style

These are the style guidelines for coding in Electron.

You can run `npm run lint` to show any style issues detected by `cpplint` and
`eslint`.

## General Code

* End files with a newline.
* Place requires in the following order:
  * Built in Node Modules (such as `path`)
  * Built in Electron Modules (such as `ipc`, `app`)
  * Local Modules (using relative paths)
* Place class properties in the following order:
  * Class methods and properties (methods starting with a `@`)
  * Instance methods and properties
* Avoid platform-dependent code:
  * Use `path.join()` to concatenate filenames.
  * Use `os.tmpdir()` rather than `/tmp` when you need to reference the
    temporary directory.
* Using a plain `return` when returning explicitly at the end of a function.
  * Not `return null`, `return undefined`, `null` or `undefined`

## C++ and Python

For C++ and Python, we follow Chromium's [Coding
Style](https://www.chromium.org/developers/coding-style). You can use
[clang-format](clang-format.md) to format the C++ code automatically. There is
also a script `script/cpplint.py` to check whether all files conform.

The Python version we are using now is Python 2.7.

The C++ code uses a lot of Chromium's abstractions and types, so it's
recommended to get acquainted with them. A good place to start is
Chromium's [Important Abstractions and Data Structures](https://www.chromium.org/developers/coding-style/important-abstractions-and-data-structures)
document. The document mentions some special types, scoped types (that
automatically release their memory when going out of scope), logging mechanisms
etc.

## Documentation

* Write [remark](https://github.com/remarkjs/remark) markdown style.

You can run `npm run lint-docs` to ensure that your documentation changes are
formatted correctly.

## JavaScript

* Write [standard](https://www.npmjs.com/package/standard) JavaScript style.
* File names should be concatenated with `-` instead of `_`, e.g.
  `file-name.js` rather than `file_name.js`, because in
  [github/atom](https://github.com/github/atom) module names are usually in
  the `module-name` form. This rule only applies to `.js` files.
* Use newer ES6/ES2015 syntax where appropriate
  * [`const`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const)
    for requires and other constants.  If the value is a primitive, use uppercase naming (eg `const NUMBER_OF_RETRIES = 5`).
  * [`let`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let)
    for defining variables
  * [Arrow functions](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions)
    instead of `function () { }`
  * [Template literals](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals)
    instead of string concatenation using `+`

## Naming Things

Electron APIs uses the same capitalization scheme as Node.js:

- When the module itself is a class like `BrowserWindow`, use `PascalCase`.
- When the module is a set of APIs, like `globalShortcut`, use `camelCase`.
- When the API is a property of object, and it is complex enough to be in a
  separate chapter like `win.webContents`, use `mixedCase`.
- For other non-module APIs, use natural titles, like `<webview> Tag` or
  `Process Object`.

When creating a new API, it is preferred to use getters and setters instead of
jQuery's one-function style. For example, `.getText()` and `.setText(text)`
are preferred to `.text([text])`. There is a
[discussion](https://github.com/electron/electron/issues/46) on this.