React JS DOM vs React Native Component Tree: A Comprehensive Technical Comparison

Introduction

React JS and React Native, while sharing core principles, differ significantly in their approach to rendering and managing UI elements. This article provides an in-depth technical comparison of the Document Object Model (DOM) used in React JS and the component tree structure employed by React Native, including React Native's new architecture.

Architectural Overview

React JS and the DOM

React JS operates within web browsers, manipulating the Document Object Model (DOM) to render and update user interfaces.

Key characteristics:

1. Virtual DOM: React JS uses a virtual DOM as an abstraction layer.
2. Reconciliation: Changes are reconciled between the virtual DOM and the actual DOM.
3. HTML Elements: UI components ultimately render to standard HTML elements.

React Native and the Component Tree

React Native, designed for mobile platforms, does not interact with a DOM. Instead, it manages a tree of native components specific to the mobile operating system (iOS or Android).

Key characteristics:

1. Native Components: UI elements are mapped to platform-specific native components.
2. Bridge: JavaScript core communicates with native modules via a bridge.
3. Shadow Tree: A shadow tree of components is maintained in C++ for layout calculations.

React Native's New Architecture

React Native is transitioning to a new architecture that significantly changes how it handles rendering and native interactions:

1. Fabric: A new rendering system that improves UI responsiveness and allows for more concurrent operations.
2. TurboModules: An enhanced native module system that provides type-safe interfaces and lazy loading capabilities.

Rendering Process

React JS

1. JSX is transpiled to React.createElement() calls.
2. Virtual DOM is updated based on state or prop changes.
3. Reconciliation algorithm compares virtual DOM with actual DOM.
4. Necessary updates are batched and applied to the real DOM.

// React JS Component

function WebButton({ onPress, title }) {

  return (

    <button onClick={onPress} className="web-button">

      {title}

    </button>

  );

}

React Native

Traditional Architecture:

1. JSX is transpiled to React.createElement() calls (similar to React JS).
2. Instead of DOM nodes, React Native creates instances of native components.
3. The shadow tree is updated for layout calculations.
4. Native UI components are updated through platform-specific APIs.

New Architecture (Fabric):

1. JSX is still transpiled to React.createElement() calls.
2. The rendering is now done in C++, allowing for more synchronous operations.
3. The shadow tree and layout calculations are more tightly integrated with the native rendering.
4. Updates can be applied more efficiently, potentially in a single frame.

// React Native Component (works with both architectures)

import { TouchableOpacity, Text } from 'react-native';

function NativeButton({ onPress, title }) {

  return (

    <TouchableOpacity onPress={onPress}>

      <Text>{title}</Text>

    </TouchableOpacity>

  );

}

Performance Implications

React JS

• Advantages:
  1. Virtual DOM minimizes actual DOM manipulations, improving performance.
  2. Batching updates reduces reflow and repaint operations.
• Challenges:
  1. Large DOMs can still lead to performance issues.
  2. Complex reconciliation can be computationally expensive.

React Native

Traditional Architecture:

• Advantages:
  1. Direct mapping to native components offers near-native performance.
  2. Shadow tree in C++ allows for efficient layout calculations.
• Challenges:
  1. Bridge communication can be a bottleneck for complex interactions.
  2. Large lists or complex animations may require additional optimization.

New Architecture:

• Advantages:
  1. Fabric allows for more synchronous operations, reducing bridge-related bottlenecks.
  2. TurboModules provide lazy loading and more efficient native module interactions.
  3. Improved type safety and potential for better performance optimizations.
• Challenges:
  1. Migration from the old architecture may require significant effort for existing apps.
  2. Developers need to learn new concepts and potentially update their coding practices.

Developer Experience and Tooling

React JS

• Familiar web development paradigms and tools.
• Rich ecosystem of web-specific libraries and frameworks.
• Browser DevTools for debugging and performance profiling.

React Native

Traditional Architecture:

• Requires understanding of mobile development concepts.
• Platform-specific APIs and components need separate handling.
• Custom tooling like React Native Debugger and platform-specific profilers.

New Architecture:

• Introduces new concepts like Fabric and TurboModules that developers need to understand.
• Improved type safety with CodeGen for better developer experience.
• Enhanced debugging capabilities, especially for native module interactions.

Code Reusability and Cross-Platform Development

Shared Concepts

Both React JS and React Native share core concepts:

• Component-based architecture
• Unidirectional data flow
• Virtual representation of the UI

Divergences

1. UI Components:

   • React JS uses HTML elements and CSS for styling.
   • React Native uses platform-specific components and a subset of CSS properties.

2. Event Handling:

   • React JS: DOM events (e.g., onClick, onChange)
   • React Native: Touch events (e.g., onPress) and custom APIs

3. Layout:

   • React JS: Flexbox, CSS Grid, and traditional CSS layouts
   • React Native: Primarily Flexbox with some limitations

4. Native Functionality:

   • React JS: Limited to web APIs and browser capabilities.
   • React Native: Access to platform-specific APIs, enhanced with TurboModules in the new architecture.

Example of divergence in layout:

// React JS

<div style={{ display: 'flex', justifyContent: 'center' }}>

  <span>Centered Content</span>

</div>

// React Native (both architectures)

import { View, Text } from 'react-native';

<View style={{ flex: 1, justifyContent: 'center', alignItems: 'center' }}>

  <Text>Centered Content</Text>

</View>

Implications for Application Architecture

React JS

• Can leverage existing web APIs and browser capabilities.
• SEO considerations may influence component structure.
• Progressive enhancement and accessibility are key concerns.

React Native

Traditional Architecture:

• Must consider platform-specific capabilities and limitations.
• Performance optimization often involves native modules or platform-specific code.
• UI consistency across platforms requires careful component design.

New Architecture:

• Allows for more efficient bridge communication, potentially simplifying complex interactions.
• TurboModules enable more granular control over native module loading and execution.
• Fabric's synchronous layout capabilities may influence component design and animation strategies.

Conclusion

The architectural differences between React JS and React Native reflect their distinct target environments. React JS manipulates the DOM for web browsers, while React Native interacts with native components on mobile platforms. React Native's new architecture with Fabric and TurboModules represents a significant evolution, addressing performance bottlenecks and enhancing developer experience.

Understanding these differences is crucial for developers working across platforms or deciding between web and native mobile development. Each approach offers unique advantages and challenges, and the choice between them should be based on project requirements, performance needs, and target audience.

As both technologies continue to evolve, we can expect further optimizations and potentially more convergence in development patterns, making it easier to build truly cross-platform applications with React technologies.