JavaScript Standards

Auto-loads for projects with JavaScript/Node.js in their tech stack.

Metadata

Field	Value
Type	context
Applies to	javascript, nodejs, express, fastify, hapi, npm, yarn, pnpm, bun, deno, vitest, jest, mocha

Core Principles

Simplicity - Simple, understandable code
Readability - Readability over cleverness
Maintainability - Code that’s easy to maintain
Testability - Code that’s easy to test
DRY - Don’t Repeat Yourself

Naming Conventions

Element	Convention	Example
Variables/Functions	camelCase	`getUserById`, `isActive`
Classes	PascalCase	`UserService`, `ApiClient`
Constants	UPPER_SNAKE_CASE	`MAX_RETRY_COUNT`
Files	kebab-case	`user-service.js`

ES Modules

// math.js - Named exports
export function add(a, b) {
    return a + b;
}
 
// app.js - Import
import { add, multiply } from './math.js';
 
// Default export
export default class UserService { }

package.json:

{
    "type": "module"
}

Async/Await

// Always use async/await
async function fetchUserData(userId) {
    const response = await fetch(`/api/users/${userId}`);
    if (!response.ok) {
        throw new Error(`API error: ${response.statusText}`);
    }
    return await response.json();
}
 
// Parallel execution
async function fetchMultipleUsers(userIds) {
    return Promise.all(userIds.map(id => fetchUserData(id)));
}

Best Practices

// Prefer const over let
const users = [];
 
// Nullish coalescing and optional chaining
const name = user?.profile?.name ?? 'Anonymous';
 
// Array methods over loops
const activeUsers = users.filter(u => u.isActive);
const userNames = users.map(u => u.name);
 
// Private class fields
class UserService {
    #apiClient;
 
    constructor(apiClient) {
        this.#apiClient = apiClient;
    }
}

Express Example

import express from 'express';
 
const app = express();
app.use(express.json());
 
app.get('/users/:id', (req, res) => {
    const { id } = req.params;
    res.json({ id, name: 'User' });
});
 
// Error handling (must be last)
app.use((err, req, res, next) => {
    console.error(err.stack);
    res.status(500).json({ error: 'Internal Server Error' });
});

Recommended Tooling

Tool	Purpose
`pnpm` or `bun`	Package manager
`eslint`	Linting
`prettier`	Code formatting
`vitest` or `jest`	Testing
`node --watch`	Development

Production Checklist

Use ES Modules ("type": "module")
Always async/await for async operations
Handle promise rejections
Validate API input
Use environment variables for config
Handle SIGTERM for graceful shutdown

TypeScript Shell/Bash