javascript-typescript-standards

name	javascript-typescript-standards
description	Guidelines for writing JavaScript and TypeScript code that is simple, readable, and maintainable. Use when working with .js, .jsx, .ts, .tsx, .mjs, .cjs files, or when the user asks about JavaScript/TypeScript coding standards, ES2022 features, Node.js modules, async/await patterns, or testing with Vitest.
metadata	{"author":"devbyray","version":"1.0","languages":"javascript, typescript","frameworks":"node.js, vitest"}

JavaScript/TypeScript Standards

Apply these standards when writing or reviewing JavaScript/TypeScript code.

Core Coding Standards

Language Features

• Use JavaScript with ES2022 features and Node.js (22+) ESM modules
• Use Node.js built-in modules and avoid external dependencies where possible
• Ask the user if you require any additional dependencies before adding them
• Always use async/await for asynchronous code

Code Quality

• Keep the code simple, readable, and maintainable
• Use descriptive variable and function names
• Do not add comments unless absolutely necessary, the code should be self-explanatory
• Never use null, always use undefined for optional values

Syntax Preferences

• Prefer functions over classes
• Use arrow functions for callbacks
• Use const for variables that are not reassigned, and let for those that are
• Use template literals for strings that require interpolation
• Use destructuring for objects and arrays where appropriate
• Use for...of loops for iterating over arrays and for...in loops for iterating over objects
• Use semicolons at the end of statements
• Prefer single quotes for strings

Component & Module Structure

• Use function-based components
• Use arrow functions for callbacks
• Organize code by feature/module
• Write clear, concise JSDoc/TSDoc comments when necessary

Testing Standards

Framework

• Use Vitest for testing

Best Practices

• Write tests for all new features and bug fixes
• Ensure tests cover edge cases and error handling
• Name tests clearly: shouldDoSomethingWhenCondition()
• NEVER change the original code to make it easier to test; instead, write tests that cover the original code as it is

Examples

Good: Modern async/await

const fetchUserData = async userId => {
	const response = await fetch(`/api/users/${userId}`)
	const data = await response.json()
	return data
}

Bad: Promises with .then()

const fetchUserData = userId => {
	return fetch(`/api/users/${userId}`)
		.then(response => response.json())
		.then(data => data)
}

Good: Descriptive names and const

const maxRetryAttempts = 3
const isValidEmail = email => /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email)

Bad: Unclear names and var

var x = 3
var check = e => /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(e)

Good: Template literals and destructuring

const getUserGreeting = ({ firstName, lastName }) => {
	return `Hello, ${firstName} ${lastName}!`
}

Bad: String concatenation

const getUserGreeting = user => {
	return 'Hello, ' + user.firstName + ' ' + user.lastName + '!'
}

When to Apply

Apply these standards when:

• Creating new JavaScript/TypeScript files
• Reviewing or refactoring existing code
• User asks about JavaScript/TypeScript best practices
• Working with Node.js projects
• Writing or reviewing tests with Vitest