How to Convert an Angular Project into Svelte

Transitioning from Angular to Svelte: A Developer's Guide

In the ever-evolving landscape of web development, the choice of frameworks and languages can significantly impact the efficiency, maintainability, and performance of applications. Angular, a robust and well-established framework, has been a popular choice among developers for building dynamic single-page applications. However, with the rise of new frameworks that promise more simplicity and speed, many developers are considering a switch. Svelte, a relatively new but increasingly popular framework, offers a unique approach by shifting much of the work to compile time, resulting in smaller bundles and faster runtime execution.

There are several reasons why a developer might want to convert from Angular to Svelte. Svelte's simplicity in syntax and smaller learning curve can lead to faster development times. Its reactive programming model is straightforward, eliminating the need for additional libraries or complex state management solutions. Moreover, Svelte applications often boast better performance due to the lack of a virtual DOM and less boilerplate code. For developers seeking to build highly interactive and performant web applications with less overhead, Svelte can be an attractive alternative to Angular.

Understanding the Differences Between Angular and Svelte

Before diving into the conversion process, it's essential to understand the fundamental differences between Angular and Svelte. The following table provides an overview of the key distinctions between the two frameworks:

Aspect	Angular	Svelte
Architecture	Component-based with services and dependency injection	Component-based with a focus on simplicity and minimalism
Reactivity	Reactive forms and RxJS for reactive programming	Built-in reactivity with simple assignment
Bundle Size	Larger, due to framework overhead	Smaller, as Svelte compiles away the framework
Learning Curve	Steeper, with a comprehensive list of concepts to grasp	Gentler, with fewer concepts and a straightforward approach
State Management	NgRx, NgXS, or other libraries for complex state management	Simple store mechanism for reactive state management

Syntax Differences Between Angular and Svelte

When converting from Angular to Svelte, developers must adapt to different syntax and paradigms. The following table highlights some of the syntax differences between the two:

Feature	Angular Syntax	Svelte Syntax
Component Definition	@Component({...})	Script tag with export default
Template Binding	{{ value }}	{value}
Event Handling	(click)="handleClick()"	on:click={handleClick}
Styling	@Component({styles: [...]})	Style tag within component
Reactivity	Use RxJS or NgModel	Assignments are reactive

Converting Angular Code to Svelte

The conversion process from Angular to Svelte involves several steps, from rethinking the application structure to rewriting components and services. Below are examples of how Angular code can be translated into Svelte syntax.

Component Definition


<!-- Angular Component -->
@Component({
  selector: 'app-greeting',
  template: `<h2>{{ greeting }}</h2>`
})
export class GreetingComponent {
  greeting = 'Hello, World!';
}

<!-- Svelte Component -->
<script>
  export default let greeting = 'Hello, World!';
</script>
<h2>{greeting}</h2>

Event Handling


<!-- Angular Event Handling -->
<button (click)="handleClick()" >Click Me</button>

@Component({...})
export class ButtonComponent {
  handleClick() {
    console.log('Button clicked in Angular');
  }
}

<!-- Svelte Event Handling -->
<script>
  function handleClick() {
    console.log('Button clicked in Svelte');
  }
</script>
<button on:click={handleClick} >Click Me</button>

Reactivity


<!-- Angular Reactivity -->
@Component({...})
export class CounterComponent {
  count = 0;

  increment() {
    this.count++;
  }
}

<!-- Svelte Reactivity -->
<script>
  let count = 0;

  function increment() {
    count++;
  }
</script>
<button on:click={increment} >+</button>
<p>{count}</p>

Converting an application from Angular to Svelte requires careful planning and understanding of both frameworks. While the syntax and concepts may differ, the fundamental principles of component-based architecture remain the same. By embracing Svelte's simplicity and performance benefits, developers can create web applications that are both powerful and easy to maintain.

Angular to Svelte Conversion Checklist

Project Setup

Initialize a new Svelte project using the Svelte template.
Remove Angular-specific files and dependencies from your project.
Install Svelte-specific dependencies such as svelte and rollup or webpack.
Configure your build tools to support Svelte (e.g., Rollup or Webpack plugins).

Component Conversion

Convert Angular components to Svelte components.
Translate Angular templates to Svelte syntax.
Refactor Angular services to Svelte stores or context.
Replace Angular directives with Svelte directives.
Adapt Angular input and output bindings to Svelte props and events.

State Management

Replace Angular's RxJS observables with Svelte stores.
Convert Angular's NgRx store to Svelte's built-in store or community solutions.

Routing

Replace Angular Router with Svelte routing solutions like svelte-routing or svelte-spa-router.

Styling

Convert global stylesheets to Svelte's scoped styling.
Adapt Angular's component styles to Svelte's style tags within components.

Testing

Replace Angular testing frameworks with Svelte-compatible ones like @testing-library/svelte or jest.
Update test cases to reflect Svelte's syntax and lifecycle.

Build and Deployment

Update CI/CD pipelines to accommodate Svelte's build process.
Ensure deployment processes are compatible with Svelte applications.

Code Examples

Below are some code snippets to help illustrate the conversion process:

Angular Component to Svelte Component

// Angular Component
@Component({
  selector: 'app-example',
  template: `Hello {{name}}`
})
export class ExampleComponent {
  name = 'World';
}

// Svelte Component
<script>
  let name = 'World';
</script>

<h3>Hello {name}</h3>

Angular Service to Svelte Store

// Angular Service
@Injectable({
  providedIn: 'root'
})
export class DataService {
  private data = new BehaviorSubject(null);
  currentData = this.data.asObservable();
  
  constructor() { }

  changeData(data: any) {
    this.data.next(data);
  }
}

// Svelte Store
<script>
  import { writable } from 'svelte/store';

  export const data = writable(null);
</script>

Options

Toggles