Style Guide - Twenty

React

Functional components only

Always use TSX functional components with named exports.

tsx

// ❌ Bad
const MyComponent = () => {
  return <div>Hello World</div>;
};
export default MyComponent;

// ✅ Good
export function MyComponent() {
  return <div>Hello World</div>;
};

Props

Create a type named {ComponentName}Props. Use destructuring. Don't use React.FC.

tsx

type MyComponentProps = {
  name: string;
};

export const MyComponent = ({ name }: MyComponentProps) => <div>Hello {name}</div>;

No single-variable prop spreading

tsx

// ❌ Bad
const MyComponent = (props: MyComponentProps) => <Other {...props} />;

// ✅ Good
const MyComponent = ({ prop1, prop2 }: MyComponentProps) => <Other {...{ prop1, prop2 }} />;

State Management

Jotai atoms for global state

tsx

import { createAtomState } from '@/ui/utilities/state/jotai/utils/createAtomState';
import { useAtomState } from '@/ui/utilities/state/jotai/hooks/useAtomState';

export const myAtomState = createAtomState<string>({
  key: 'myAtomState',
  defaultValue: 'default value',
});

Prefer atoms over prop drilling
Don't use useRef for state — use useState or atoms
Use atom families and selectors for lists

Avoid unnecessary re-renders

Extract useEffect and data fetching into sibling sidecar components
Prefer event handlers (handleClick, handleChange) over useEffect
Don't use React.memo() — fix the root cause instead
Limit useCallback / useMemo usage

tsx

// ❌ Bad — useEffect in the same component causes re-renders
export const Page = () => {
  const [data, setData] = useAtomState(dataState);
  const [dep] = useAtomState(depState);
  useEffect(() => { setData(dep); }, [dep]);
  return <div>{data}</div>;
};

// ✅ Good — extract into sibling
export const PageData = () => {
  const [data, setData] = useAtomState(dataState);
  const [dep] = useAtomState(depState);
  useEffect(() => { setData(dep); }, [dep]);
  return <></>;
};
export const Page = () => {
  const [data] = useAtomState(dataState);
  return <div>{data}</div>;
};

TypeScript

type over interface — more flexible, easier to compose
String literals over enums — except for GraphQL codegen enums and internal library APIs
No any — strict TypeScript enforced
No type imports — use regular imports (enforced by Oxlint typescript/consistent-type-imports)
Use Zod for runtime validation of untyped objects

JavaScript

tsx

// Use nullish-coalescing (??) instead of ||
const value = process.env.MY_VALUE ?? 'default';

// Use optional chaining
onClick?.();

Naming

Variables: camelCase, descriptive (email not value, fieldMetadata not fm)
Constants: SCREAMING_SNAKE_CASE
Types/Classes: PascalCase
Files/directories: kebab-case (.component.tsx, .service.ts, .entity.ts)
Event handlers: handleClick (not onClick for the handler function)
Component props: prefix with component name (ButtonProps)
Styled components: prefix with Styled (StyledTitle)

Styling

Use Linaria styled components. Use theme values — avoid hardcoded px, rem, or colors.

tsx

// ❌ Bad
const StyledButton = styled.button`
  color: #333333;
  font-size: 1rem;
  margin-left: 4px;
`;

// ✅ Good
const StyledButton = styled.button`
  color: ${({ theme }) => theme.font.color.primary};
  font-size: ${({ theme }) => theme.font.size.md};
  margin-left: ${({ theme }) => theme.spacing(1)};
`;

Imports

Use aliases instead of relative paths:

tsx

// ❌ Bad
import { Foo } from '../../../../../testing/decorators/Foo';

// ✅ Good
import { Foo } from '~/testing/decorators/Foo';
import { Bar } from '@/modules/bar/components/Bar';

Folder Structure

front
└── modules/         # Feature modules
│   └── module1/
│       ├── components/
│       ├── constants/
│       ├── contexts/
│       ├── graphql/  (fragments, queries, mutations)
│       ├── hooks/
│       ├── states/   (atoms, selectors)
│       ├── types/
│       └── utils/
└── pages/           # Route-level components
└── ui/              # Reusable UI components (display, input, feedback, ...)

Modules can import from other modules, but ui/ should stay dependency-free
Use internal/ subfolders for module-private code
Components under 300 lines, services under 500 lines