Facebook’s open source JavaScript library React has been released in version 17. 0. The makers behind it had already announced in August this year, when the release candidate appeared, that the new release would not contain any new features relevant to developers. Instead, the focus is probably on making the upgrade of React easier itself.

Gradual upgrading Although they are developing new functions, React 17 was about creating the basis for introducing innovations without anyone being left behind. The new release is supposed to make it safer to embed a directory tree managed by one React version in another one managed by another version.

With React 17 React upgrades are now possible in stages. Who upgraded from React 15 to the version 16 (or from React 16 to 17), used to update the entire application at once. This turns out to be difficult if the code base has not been actively maintained for a long time. From now on, however, you will have more options with React 18 and other future versions. You can certainly still update the entire application at once. But an application can also be transferred piece by piece.

To enable the gradual updates, some changes to the React event system were necessary. These, like some other changes, can apparently lead to compatibility problems. React will no longer use event handlers on the document level. Instead they are attached to the root DOM container in which the React tree is rendered:

const rootNode = document.getElementById (‘root’) ;

ReactDOM.render (, rootNode); resulted in React 16 and earlier React for most events document.addEventListener () . With React 17 instead rootNode.addEventListener () called under the hood.

A new JSX transformation React 17 finally supports a new JSX-T