TypeScript Best Practices#

Code Style#

• Use strict mode ("strict": true in tsconfig.json)
• Prefer interface over type for object shapes
• Use const by default, let when needed, never var
• Enable noImplicitAny and strictNullChecks

Type Safety#

// GOOD: Explicit types and null handling
function getUser(id: string): User | undefined {
    return users.get(id);
}

const user = getUser(id);
if (user) {
    console.log(user.name);  // TypeScript knows user is defined
}

// BAD: Type assertions to bypass safety
const user = getUser(id) as User;  // Dangerous if undefined
console.log(user.name);  // Might crash

Error Handling#

• Use try/catch for async operations
• Define custom error types for domain errors
• Never swallow errors silently

Security#

• Validate all user input at API boundaries
• Use parameterized queries for database operations
• Sanitize data before rendering in DOM (prevent XSS)
• Never use eval() or Function() with user input