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Petr Janik
Petr Janik

Posted on • Updated on

Classes vs Functional components in React

In React, we can either use classes or functions for our components.

Classes

As you may have noticed in the first part of this series, we can create a React component as a class. To do so, we have to extend a React.Component class and implement its render() method.
This method must return either one root element or a fragment.

  • This class renders a <div> and its contents.
export default class TodoList extends React.Component {
  render() {
    return (
      <div>
        <h1>Todo list</h1>
      </div>
    );
  }
}
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  • This class renders a fragment.
export default class TodoList extends React.Component {
  render() {
    return (
      <>
        <h1>Todo list</h1>
        <h1>Second element</h1>
      </>
    );
  }
}
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Alternatively

export default class TodoList extends React.Component {
  render() {
    return (
      <React.Fragment>
        <h1>Todo list</h1>
        <h1>Second element</h1>
      </React.Fragment>
    );
  }
}
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Using fragments enables us to have multiple elements on the same level without having any <div> around them.

Functions

Instead of classes, we can write our components as functions.
The rules for the export and import are the same as with classes.
The function itself must return either one root element or a fragment.

Default export

  • Named function
export default function TodoList() {
  return (
    <div>
      <h1>Todo list</h1>
    </div>
  );
}
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  • Anonymous function

When using default export, we may omit the name completely.
However, I do not recommend this.

export default function () {
  return (
    <div>
      <h1>Todo list</h1>
    </div>
  );
}
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  • Named arrow function
const TodoList = () => {
  return (
    <div>
      <h1>Todo list</h1>
    </div>
  );
};

export default TodoList;
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  • Anonymous arrow function
export default () => {
  return (
    <div>
      <h1>Todo list</h1>
    </div>
  );
};
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Named export

  • Named function
export function TodoList() {
  return (
    <div>
      <h1>Todo list</h1>
    </div>
  );
}
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  • Named arrow function
export const TodoList = () => {
  return (
    <div>
      <h1>Todo list</h1>
    </div>
  );
};
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Another not so fashionable option could be

export const TodoList = function () {
  return (
    <div>
      <h1>Todo list</h1>
    </div>
  );
};
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Personally, I prefer writing the React components as arrow functions.

Top comments (2)

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asher_dev profile image
Asher

There is one caveat, however. Using default export of the arrow function is only possible after the declaration.

You could just export default anonymous arrow function



export default () => {
  return ( <h1>Hello World</h1> )
}
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petr7555 profile image
Petr Janik Author

Thank you, I have corrected it.

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Sorry, it's true.