Difference Between React JS version 16, 17 and 18

React has evolved significantly over its major versions, with each release introducing new features and improvements. Here’s a summary of the key differences between React 16, 17, and 18:

React 16

Release Date: September 2017

Key Features:

• Fiber Architecture: Introduced a complete rewrite of the React core algorithm, improving rendering performance and enabling features like time-slicing.
  
  
• Error Boundaries: Introduced a way to catch JavaScript errors in components and display a fallback UI.
  
  
• Fragments: Allowed developers to return multiple elements from a component without adding extra nodes to the DOM.
  
  
• Portals: Enabled rendering children into a DOM node that exists outside the parent component's hierarchy.
  
  
• Context API: A new context API was introduced to facilitate easier data sharing between components without prop drilling.
  
  
• Lazy Loading: Introduced React.lazy() and Suspense for code-splitting and lazy loading of components.
  
  

React 17

Release Date: October 2020

Key Features:

• No New Features: This version focused primarily on making it easier to upgrade React itself and improve the upgrade process.
  
  
• Gradual Upgrades: Allowed for gradual upgrades by enabling multiple versions of React to exist on the same page, facilitating easier migrations.
  
  
• Event Delegation: Improved event delegation for better performance and to reduce issues related to event handling across components.
  
  
• Support for New JSX Transform: Supported the new JSX transform introduced by React 17, which allows you to use JSX without importing React in every file.
  
  

React 18

Release Date: March 2022

Key Features:

• Concurrent Features: Introduced features that allow React to work on multiple tasks at once, improving responsiveness and rendering performance.
  
  
• Automatic Batching: Updated batching of state updates to allow multiple state updates in a single render, which can improve performance.
  
  
• startTransition API: Introduced a new API to mark updates as non-urgent, enabling smoother transitions for less critical updates.
  
  
• Suspense for Data Fetching: Expanded Suspense to handle data fetching, allowing for better management of loading states in async components.
  
  
• useId Hook: Introduced a new hook for generating unique IDs for accessibility and client/server rendering consistency.
  
  
• Concurrent Rendering: Added the ability to render components in a way that doesn’t block the main thread, enhancing user experience.
  
  

Summary of Differences

Feature	React 16	React 17	React 18
Architecture	Fiber architecture	Focused on upgrade process	Concurrent features
Error Handling	Error Boundaries	No major changes	No major changes
Context API	Improved context API	No major changes	No major changes
Code Splitting	React.lazy and Suspense	No major changes	Enhanced Suspense for data
Event Handling	Standard event delegation	Improved delegation	No major changes
JSX Transform	No	Supported new transform	Supported new transform
Performance Improvements	Time-slicing	Gradual upgrades	Automatic batching
New APIs	Portals, Fragments	None	startTransition, useId

Conclusion

• React 16 laid the foundation with new architectural improvements and core features.
  
  
• React 17 focused on enhancing the upgrade process and ensuring smoother transitions.
  
  
• React 18 introduced significant performance improvements with concurrent features and better handling of asynchronous rendering.