React Academy · Lesson

Generic Components & Utility Types

Write reusable generic components and use PropsWithChildren, ComponentProps, and Omit.

Generic Components & Utility Types is a free React Academy lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the React Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Why Generic Components?

Generic components adapt to different data types while staying fully type-safe — a typed list, select, or table that works with any data shape.

A Simple Generic List

Use a type parameter T on the function to make a list component that renders any item type.

interface ListProps<T> {
  items: T[];
  renderItem: (item: T, index: number) => React.ReactNode;
  keyExtractor: (item: T) => string;
}

function List<T>({ items, renderItem, keyExtractor }: ListProps<T>) {
  return (
    <ul>
      {items.map((item, i) => (
        <li key={keyExtractor(item)}>{renderItem(item, i)}</li>
      ))}
    </ul>
  );
}

Constraining Generic Types

Use extends to add constraints so TypeScript knows what properties the type must have.

interface SelectProps<T extends { id: string; label: string }> {
  options: T[];
  value: T | null;
  onChange: (option: T) => void;
}

function Select<T extends { id: string; label: string }>(
  { options, value, onChange }: SelectProps<T>
) {
  return (
    <select value={value?.id} onChange={e => onChange(options.find(o => o.id === e.target.value)!)}>
      {options.map(o => <option key={o.id} value={o.id}>{o.label}</option>)}
    </select>
  );
}

PropsWithChildren

React.PropsWithChildren<P> adds children?: React.ReactNode to any props type — useful for wrapper components.

function Card({ title, children }: React.PropsWithChildren<{ title: string }>) {
  return (
    <div className="card">
      <h2>{title}</h2>
      {children}
    </div>
  );
}

ComponentProps

React.ComponentProps<typeof Component> extracts the props of an existing component, useful when you want to extend or wrap it.

import { Button } from './Button';

type ExtendedButtonProps = React.ComponentProps<typeof Button> & {
  loading?: boolean;
};

function LoadingButton({ loading, children, ...props }: ExtendedButtonProps) {
  return (
    <Button {...props} disabled={loading || props.disabled}>
      {loading ? <Spinner /> : children}
    </Button>
  );
}

ComponentPropsWithoutRef

React.ComponentPropsWithoutRef<'input'> extracts HTML element props without the ref prop — ideal for wrapping HTML elements.

type InputProps = React.ComponentPropsWithoutRef<'input'> & {
  label: string;
  error?: string;
};

function FormInput({ label, error, ...inputProps }: InputProps) {
  return (
    <div>
      <label>{label}</label>
      <input {...inputProps} />
      {error && <span className="error">{error}</span>}
    </div>
  );
}

Omit & Pick

Use Omit<T, Keys> to remove specific props and Pick<T, Keys> to keep only specific props from an existing type.

interface UserCardProps {
  id: string;
  name: string;
  email: string;
  avatar: string;
  role: string;
}

// Only expose non-sensitive fields:
type PublicUserCardProps = Omit<UserCardProps, 'email' | 'role'>;
// Or pick exactly what you need:
type AvatarProps = Pick<UserCardProps, 'name' | 'avatar'>;

Partial & Required

Partial<T> makes all props optional (useful for update forms). Required<T> makes all props required.

interface UserFormData { name: string; email: string; bio: string; }

// For update: only send changed fields
type UserUpdatePayload = Partial<UserFormData>;

// For create: all fields are mandatory
type UserCreatePayload = Required<UserFormData>;

Record for Typed Dictionaries

Record<Keys, Value> creates an object type with specific key types, useful for lookup maps and translations.

type Status = 'idle' | 'loading' | 'success' | 'error';

const statusLabels: Record<Status, string> = {
  idle: 'Ready',
  loading: 'Loading...',
  success: 'Done!',
  error: 'Something went wrong',
};

ReturnType for Hook Types

Use ReturnType<typeof useMyHook> to infer the return type of a custom hook without manually duplicating the type.

function useCounter(initial: number) {
  const [count, setCount] = useState(initial);
  return { count, increment: () => setCount(c => c + 1) };
}

type CounterHook = ReturnType<typeof useCounter>;
// { count: number; increment: () => void }

Generic Table Component

A fully type-safe data table that works with any row shape, infers column keys, and still provides autocomplete.

interface Column<T> {
  key: keyof T;
  header: string;
  render?: (value: T[keyof T], row: T) => React.ReactNode;
}

function DataTable<T extends object>({ data, columns }: { data: T[]; columns: Column<T>[] }) {
  return (
    <table>
      <thead><tr>{columns.map(c => <th key={String(c.key)}>{c.header}</th>)}</tr></thead>
      <tbody>{data.map((row, i) => (
        <tr key={i}>{columns.map(c => <td key={String(c.key)}>{c.render ? c.render(row[c.key], row) : String(row[c.key])}</td>)}</tr>
      ))}</tbody>
    </table>
  );
}

Quick Check

Which utility type removes specified keys from an existing TypeScript interface?

Recap

Generic components use type parameters to stay type-safe across data shapes. Utility types like Omit, Pick, Partial, ComponentProps, and PropsWithChildren eliminate manual type duplication and make component APIs more composable.

Frequently asked questions

Is the “Generic Components & Utility Types” lesson free?

Yes — the full text of “Generic Components & Utility Types” is free to read here on the web, and the React Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the React Academy course, upgrade to CoddyKit PRO.

What will I learn in “Generic Components & Utility Types”?

Write reusable generic components and use PropsWithChildren, ComponentProps, and Omit. You practise React Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start React Academy?

No prior experience is required. React Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Generic Components & Utility Types” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this React Academy lesson?

Yes. Every React Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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