Svelte vs TDI2

TDI2 and Svelte 5 both solve the same fundamental problem: eliminating component state hell through automatic reactivity. While Svelte requires a new framework, TDI2 brings similar benefits to existing React applications.

Core Philosophy Comparison

Both eliminate the complexity of manual state management, but through different architectural approaches:

Aspect	Svelte 5 Runes	TDI2 + Valtio
Architecture	Framework-level reactivity	Library-level reactivity within React
State Location	$state() objects	Service state objects (Valtio proxies)
Components	Pure templates	Pure templates with service injection
Reactivity	Built-in proxy reactivity	Valtio proxy reactivity via useSnapshot
Migration	Full rewrite required	Gradual adoption in existing React apps
TypeScript	Good support	Full TypeScript integration with interfaces
Ecosystem	Svelte ecosystem	React ecosystem compatibility

Side-by-Side Code Comparison

Simple Counter Example

Svelte 5:

<script>
  let counter = $state({
    count: 0,
    message: "Click to count!"
  });

  function increment() {
    counter.count++;
    counter.message = `Count is now ${counter.count}`;
  }

  // Derived state
  let isEven = $derived(counter.count % 2 === 0);
</script>

<div>
  <h2>{counter.count}</h2>
  <p>{counter.message}</p>
  <p>Number is {isEven ? 'even' : 'odd'}</p>
  <button onclick={increment}>+</button>
</div>

TDI2:

// Service with Valtio reactive state
@Service()
export class CounterService implements CounterServiceInterface {
  state = {
    count: 0,
    message: "Click to count!"
  };

  increment(): void {
    this.state.count++;
    this.state.message = `Count is now ${this.state.count}`;
  }

  get isEven(): boolean {
    return this.state.count % 2 === 0;
  }
}

// Pure React component template
function Counter({ counterService }: { counterService: Inject<CounterServiceInterface> }) {
  const { count, message } = counterService.state;
  const { isEven } = counterService;

  return (
    <div>
      <h2>{count}</h2>
      <p>{message}</p>
      <p>Number is {isEven ? 'even' : 'odd'}</p>
      <button onClick={() => counterService.increment()}>+</button>
    </div>
  );
}

Key Similarity: Both eliminate the need for useState, useEffect, and manual state synchronization.

Complex E-Commerce Example

Shopping Cart with Cross-Component State

Svelte 5:

CartStore.svelte.js

<script>
  let cartState = $state({
    items: [],
    total: 0
  });

  export function addItem(product) {
    cartState.items = [...cartState.items, product];
    cartState.total = cartState.items.reduce((sum, item) => sum + item.price, 0);
  }

  export function removeItem(productId) {
    cartState.items = cartState.items.filter(item => item.id !== productId);
    cartState.total = cartState.items.reduce((sum, item) => sum + item.price, 0);
  }

  export { cartState };
</script>

<!-- ProductList.svelte -->
<script>
  import { cartState, addItem } from './CartStore.svelte.js';

  let products = [
    { id: 1, name: 'iPhone', price: 999 },
    { id: 2, name: 'MacBook', price: 1999 }
  ];
</script>

<div>
  {#each products as product}
    <div>
      <h3>{product.name} - ${product.price}</h3>
      <button onclick={() => addItem(product)}>Add to Cart</button>
    </div>
  {/each}
  <p>Cart Total: ${cartState.total}</p>
</div>

TDI2:

// Business Logic Service
@Service()
export class CartService implements CartServiceInterface {
  state = {
    items: [] as CartItem[],
    total: 0
  };

  addItem(product: Product): void {
    this.state.items.push({ ...product, quantity: 1 });
    this.calculateTotal();
  }

  removeItem(productId: string): void {
    this.state.items = this.state.items.filter(item => item.id !== productId);
    this.calculateTotal();
  }

  private calculateTotal(): void {
    this.state.total = this.state.items.reduce((sum, item) => sum + item.price, 0);
  }
}

// Pure Template Component
function ProductList({
  productService,
  cartService
}: {
  productService: Inject<ProductServiceInterface>;
  cartService: Inject<CartServiceInterface>;
}) {
  const { products } = productService.state;
  const { total } = cartService.state;

  return (
    <div>
      {products.map(product => (
        <div key={product.id}>
          <h3>{product.name} - ${product.price}</h3>
          <button onClick={() => cartService.addItem(product)}>
            Add to Cart
          </button>
        </div>
      ))}
      <p>Cart Total: ${total}</p>
    </div>
  );
}

Key Differences

1. Migration Strategy

Svelte 5:

• Requires complete rewrite from React
• Cannot coexist with existing React components
• All-or-nothing adoption decision

TDI2:

• Gradual migration from existing React
• Can coexist with traditional React patterns
• Component-by-component adoption possible

2. Ecosystem Integration

Svelte 5:

<!-- Limited to Svelte ecosystem -->
<script>
  import { onMount } from 'svelte';
  // Svelte-specific libraries and patterns
</script>

TDI2:

// Full React ecosystem compatibility
@Service()
export class DataService {
  constructor(
    @Inject() private apiClient: AxiosInstance, // Any React library
    @Inject() private router: NextRouter,        // Next.js integration
    @Inject() private analytics: GTM            // Google Analytics
  ) {}
}

3. Testing Approach

Svelte 5:

// Svelte Testing Library
import { render, fireEvent } from '@testing-library/svelte';
import Counter from './Counter.svelte';

test('increments counter', async () => {
  const { getByRole, getByText } = render(Counter);
  const button = getByRole('button');

  await fireEvent.click(button);
  expect(getByText('1')).toBeInTheDocument();
});

TDI2:

// Standard React Testing Library + Service Mocking
describe('Counter', () => {
  it('increments counter', () => {
    const mockCounterService = {
      state: { count: 0 },
      increment: jest.fn()
    };

    render(<Counter counterService={mockCounterService} />);
    fireEvent.click(screen.getByRole('button'));

    expect(mockCounterService.increment).toHaveBeenCalled();
  });
});

4. Performance Characteristics

Svelte 5:

• Compile-time optimization
• No virtual DOM overhead
• Smaller runtime bundle

TDI2:

• React’s virtual DOM (with optimizations)
• Service-level memoization
• Larger runtime (React + TDI2 + Valtio)

When to Choose Each

Choose Svelte 5 When:

✅ Starting new projects from scratch ✅ Performance is critical (mobile, embedded)
✅ Team is open to new framework adoption ✅ Bundle size matters more than ecosystem ✅ Simple to moderate complexity applications

Choose TDI2 When:

✅ Existing large React codebase needs gradual improvement ✅ React ecosystem dependencies are essential ✅ Team expertise in React is significant investment ✅ Enterprise requirements need mature ecosystem ✅ Complex state management across many components ✅ TypeScript-first development with full interface support

Hybrid Approach Consideration

For teams evaluating both, consider this migration path:

1. Phase 1: Introduce TDI2 to existing React app for complex state management
2. Phase 2: Evaluate TDI2’s impact on development velocity and code quality
3. Phase 3: Consider Svelte 5 for new microservices or standalone applications
4. Phase 4: Gradual migration to Svelte 5 if performance requirements demand it

Conclusion

Svelte 5 and TDI2 validate the same architectural insight: Manual component state management is the primary source of complexity in modern UI frameworks.

• Svelte 5 solves this with a new framework and compile-time magic
• TDI2 solves this by bringing service-oriented architecture to React

Both eliminate useState hell, both provide automatic reactivity, both create pure template components. The choice depends on your migration constraints and ecosystem requirements.

For existing React teams: TDI2 provides 80% of Svelte’s reactivity benefits without the migration cost.

For new projects: Both are excellent choices - Svelte for maximum performance, TDI2 for React ecosystem compatibility.