How to Add a key to React Fragment

In this post, we will learn how to add a key to a React Fragment. Fragments are useful for grouping elements without adding extra nodes to the DOM. While using them with the concise syntax <> </> is common, adding a key prop becomes tricky.

The Traditional Syntax for Adding a Key

To add a key to a React fragment, we’ll use the traditional syntax:

<React.Fragment key={uniqueKey}>
    {/* item content here */}
</React.Fragment>

This syntax allows us to achieve the same result of grouping elements without introducing additional DOM nodes.

Let’s look at a practical example:

import React from "react";
import "./App.css";

const App = () => {
  const items = ["Apple", "Banana", "Cherry", "Date", "Elderberry"];

  return (
    <div className="container">
      {items.map((item, index) => (
        <React.Fragment key={index}>
          <p className="item-text">{item}</p>
        </React.Fragment>
      ))}
    </div>
  );
};

export default App;

Here, we’ve used the traditional syntax for React Fragments to add a key prop. This approach allows us to group elements in a list without adding extra DOM nodes.

Using the Fragment Element

If we prefer a more concise approach, we can import the Fragment element from React:

import React, { Fragment } from "react";
import "./App.css";

const App = () => {
  const items = ["Apple", "Banana", "Cherry", "Date", "Elderberry"];

  return (
    <div className="container">
      {items.map((item, index) => (
        <Fragment key={index}>
          <p className="item-text">{item}</p>
        </Fragment>
      ))}
    </div>
  );
};

export default App;

Using Fragment from the React package achieves the same result but with a more concise import statement.

When adding keys to React fragments, remember these best practices:

1. Each key within a list of fragments must be unique. Repeating keys will trigger an “Encountered two children with the same key” warning.

2. Avoid attempting to access the key property as a prop within your components. Doing so will result in an “undefined” warning since key is a reserved property for React’s internal use.

Conclusion

In conclusion, adding a key to a React fragment is a crucial step for optimizing our React app. Whether we opt for the traditional or concise syntax, understanding key prop best practices will help us build robust, high-performance React components.