git-hardening/.crosslink/rules/javascript.md

JavaScript Best Practices

Code Style

• Use const by default, let when needed, never var
• Use arrow functions for callbacks
• Use template literals over string concatenation
• Use destructuring for object/array access

Error Handling

// GOOD: Proper async error handling
async function fetchUser(id) {
    try {
        const response = await fetch(`/api/users/${id}`);
        if (!response.ok) {
            throw new Error(`HTTP ${response.status}`);
        }
        return await response.json();
    } catch (error) {
        console.error('Failed to fetch user:', error);
        throw error;  // Re-throw or handle appropriately
    }
}

// BAD: Ignoring errors
async function fetchUser(id) {
    const response = await fetch(`/api/users/${id}`);
    return response.json();  // No error handling
}

Security

• Never use eval() or innerHTML with user input
• Validate all input on both client and server
• Use textContent instead of innerHTML when possible
• Sanitize URLs before navigation or fetch