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Few Breaking Changes that are shipped with React v17 2728 Views Apr 23, 2021

Few Breaking Changes that are shipped with React v17

React.js development is the hottest topic in the software industry. React is a library developed and maintained by the Facebook team. React is one of the fastest-growing libraries, thanks to its strong corporate support and widespread interest in the JS community. 

Learning about the new versions developed by the React team can be beneficial because:

  • Deprecated code is preferable to stand the test of time rather than spending time upgrading it later.
  • Being unaware of an existing bug can lead to a significant amount of frustration while attempting to debug and fix something in the framework.
  • While deciding on a technology stack, the changes can help you make a better decision.

The React team decided that version 17 will lay the groundwork for a new method of updating. When React v18 will be released, developers will be able to upgrade only parts of their application while keeping the rest running on version 17. React advises against this if your application is actively maintained or in large-scale production. It can assist teams that do not actively maintain their application or do not need to migrate certain components to the newer version. In the future, new React versions will not abandon these applications or necessitate massive migrations.

What is new in React v17?

Progressive Upgrade 

Upgrade React gracefully and drive adoption as you see fit. Loading two versions of React, even if one is loaded lazily on-demand, is not ideal.

For most applications, upgrading all at once is still the best option. However, for larger applications, the gradual update ensures that new code can be written in React v17 without affecting the legacy code.

Import React Implicitly

There is no need to explicitly import React and manage the JSX because the React v17 compiler includes a new dependency from React-runtime that handles the JSX transformation. Your compiled bundled output will be slightly smaller as a result of this React import omission.

Handling of Events

The event handlers in React v17 will no longer be attached at the document level, but will instead be attached to the DOM container where the tree was rendered from. It is now safe to nest application’s built with different versions of React. Also, if the application’s outer shell is written in jQuery but the new code inside is written in React, |thee.stopPropagation()| will prevent it from reaching the jQuery code.

Compatibility with Browsers

React v17 has introduced a few changes to the event system. The fundamental behavior that has changed is as follows:

  • The onScroll event no longer bubbles.
  • Internally, the onBlur and onFocus events now use native focusin and focusout events, better matching React’s existing behavior and even providing more information.
  • Actual browser capture phase listeners are now used by onClickCapture.

Under the hood, the switch from focus to focusin is still the bubbling behavior for the onFocus event. The onFocus event has always bubbled in React, and it will continue to do so because it is more useful.

There are No Synthetic Events

Due to ongoing confusion and the fact that it does not improve performance, the old event pooling optimization has been removed from React. Previously, you had to call |e.persist()| to properly use the event or read the property you required. For performance in older browsers, React reused the event objects between different events and set all event fields to null in between them.

Timing of Effect Cleanup

The new version of React improves the consistency of the useEffect hook cleanup function timing. React specifically checks |setState| on unmounted components and does not issue |setState| warnings in the brief period between unmounting and cleanup. As a result, code canceling requests or intervals can almost always remain the same.

The effect cleanup function in React v17 always runs asynchronously. For instance, if the component is unmounting, the cleanup is performed after the screen has been updated.

Undefined Error Handling

Functions that return undefined always throw an error in React v16, owing to how easy it is to return undefined unintentionally.

Initially, the behavior was limited to the class and function components, but with React v17, the forward Ref and memo components were added, bringing their behavior in line with that of a regular class and function components. In addition, in cases where you would render nothing on purpose, null will be returned instead.

Stacks of Native Components

When there was an error, React 16 printed component stacks but they were inferior to the native JavaScript stacks. However, in React v17, component stacks are generated using a completely different mechanism than the regular native JavaScript stacks. In a production environment, this allows us to obtain fully symbolic React component stack traces.

There are No Private Exports

React Native’s private exports were only used in the Web project. This means that older versions of React Native for Web will not work with React 17, but newer versions will. In any case, React Native for Web has a different release cycle and will adapt to this change. 

React v17 serves as a link between the old and the upcoming new React. In addition, the team recently released Zero-Bundle-Size React Server Components.

The stepping stone release provides many reasons for React developers to be excited. It not only has some fantastic, revolutionary functionality that will reshape how React applications are designed, but it also builds on recently implemented functionality like Hooks with gradual improvements that allow developers to make better use of them. Also, while developing an OTT platform in React Native, you can use the same codebase across platforms such as Android, iOS, Apple TV, Android TV/AFTV, and Windows.


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