react-types.ts

import React, { useState } from 'react';

// types and interfaces for props
type DashboardProps = {
  totalSales: number;
};

const Dashboard: React.FC<DashboardProps> = (props) => (
  <section>
    <p>Total Sales: {props.totalSales}</p>
  </section>
);

// types applied directly to props
type Customer = {
  name: string;
  email: string;
};

type CustomerListProps = {
  customers: Customer[];
};

const CustomerList = (props: CustomerListProps) => (
  <section>
    {props.customers.map((c: Customer, i: number) => (
      <div key={i}>
        <p>{c.name}</p>
        <p>{c.email}</p>
      </div>
    ))}
  </section>
);

// event types
type DropzoneProps = {
  onDragOver: React.DragEventHandler;
};

const Dropzone: React.FC<DropzoneProps> = (props) => {
  return (
    <div style={{ border: '2px dotted #ccc' }} onDragOver={props.onDragOver}>
      <p>Welcome to the dropzone</p>
    </div>
  );
};

// generic passed to useState
type AccountDetails = {
  username: string;
};
interface AccountSettingsProps {
  accountDetails: AccountDetails;
}

const AccountSettings: React.FC<AccountSettingsProps> = (props) => {
  const [accountDetails, setAccountDetails] = useState<AccountDetails>(props.accountDetails);

  return (
    <section>
      <p>{accountDetails.username}</p>
      <form>
        <label>Set Username</label>
        <input
          placeholder="Update Username"
          onChange={(event: React.ChangeEvent<HTMLInputElement>) => {
            setAccountDetails({
              username: event.target.value
            });
          }}
        />
      </form>
    </section>
  );
};

// types for children of a component.
// there's debate over which to use.
interface ContainerProps {
  // children: React.ReactNode;
  children: React.ReactChild;
  // children: React.ReactElement;
}

const Container: React.FC<ContainerProps> = (props) => {
  return <div style={{ outline: '1px solid', padding: '10px' }}>{props.children}</div>;
};

function App() {
  return (
    <div>
      <Dashboard totalSales={10000} />
      <CustomerList customers={[{ name: 'John Doe', email: 'john@doe.com' }]} />
      <Dropzone onDragOver={(e) => console.log('on drag', e.clientX, e.clientY)} />
      <AccountSettings
        accountDetails={{
          username: 'John Doe'
        }}
      />
      <Container>
        This text works of we use React.ReactChild or 
        React.ReactNode, but not if we use React.ReactElement
      </Container>
    </div>
  );
}

export default App;