with-class.jsx

export class UserList extends React.Component {
  handleClick = (item) => console.log('You clicked ', this.props.group);
  
  render() {
    return (
      <HugeListOfItems
        group={group}
        handleClick={this.handleClick}
      />
    );
  }
}

with-hooks.jsx

export function UserList({ group }) {
  // Have to remember to useCallback here to avoid
  // the function getting recreated.
  const handleClick = useCallback(item => { 
    console.log('You clicked ', group);
    
    // Have to pass all of the variable references here so 
    // React knows when to update the callback function.
  }, [group]);

  return (
    <HugeListOfItems
      group={group}
      handleClick={handleClick}
    />
  );
}