---
title: Code Styleguide — JavaScript
last_modified: 2026-02-22
---

1. Use `const` for all declarations, unless you need to reassign, then use `let`. Never use
   `var`.

2. Indentation: Use 2 spaces.  Do not use tabs.

3. Semicolons shoudl be used at the end of statements.

4. Quotes: Prefer single quotes for strings, unless working with JSON or needing to separate object strings.

5. Limit lines to approximately 80 characters for better readability.

6. Brace Placement: Place the opening brace on the same line as the statement (e.g., if (true) {).

7. Naming Conventions:
   
   Variables, properties, and functions use lowerCamelCase.
   Class names use UpperCamelCase (PascalCase).
   Constants use UPPERCASE_WITH_UNDERSCORES. 

8. Equality: Always use the strict equality operator (===) over the abstract equality operator (==).

9. Use npm for package management, avoid using yarn.

10. Use nvm and install/select the most current LTS Node version.

11. Use `prettier` for code formatting, with four spaces for indentation.

12. At a minimum, both `npm run test`/`npm run build` should work (complete the appropriate scripts in `package.json`). However, prefer `make test` and `make build` instead —

13. The Makefile is authoritative on how to interact with the repo. See
   [Repository Policies](https://github.com/kjannette/LLM_DEV_PROMPTS/blob/master/REPO_POLICIES.md) for details.

14. Use UNIX-style newlines (\n), and a newline character as the last character of a file. Windows-style newlines (\r\n) are forbidden inside any Node/JS repository.

15. Declare one variable per statement:

**Correct:**

```
   const keys   = ['foo', 'bar'];
   const values = [23, 42];
   const object = {};
```
**Incorrect:**

```
const keys = ['foo', 'bar'],
      values = [23, 42],
      object = {},
```

16.  Name closures in order to produce better stack traces, heap and cpu profiles.

**Correct:**

```
req.on('end', function onEnd() {
  console.log('winning');
});
```
**Incorrect:**

```
req.on('end', function() {
  console.log('losing');
});
```

# Author

[@sjDev](https://sjdev.co)
<[sj@sjdev.co](mailto:sj@sjdev.co)>

# License

MIT. See [LICENSE](../LICENSE).