Svelte 3 has emerged as a compelling alternative to popular frameworks like React, Angular, and Vue, offering developers a simpler and more efficient way to create interactive web applications. With the recent release of Svelte 3, this framework has gained traction for its innovative approach to building user interfaces. In this article, we’ll explore the key concepts of Svelte 3, its unique features, and guide you through building a fullstack real-time todo application.

What is Svelte 3?

Svelte is a modern JavaScript framework that differentiates itself by compiling components at build time, rather than relying on a framework in the browser at runtime. This results in smaller code bundles, faster load times, and an overall improved user experience. Unlike other frameworks that require heavy dependencies, Svelte’s compiler generates highly optimized code that runs natively in the browser, making it an appealing choice for developers looking to streamline their applications.

Key Features of Svelte 3

1. Compiler-Based Architecture

Svelte operates using a compiler that transforms your components into efficient JavaScript code during the build process. This means that the framework doesn’t need to be included with your final bundle, leading to reduced size and improved performance.

2. Reactive Programming Model

Svelte’s reactivity is straightforward and intuitive. Variable assignments automatically trigger DOM updates, making it easy to manage state without the need for additional libraries or complex setups. You can use the simple assignment operator for reactivity, which ensures better performance and less boilerplate code.

3. Scoped Styles

Each component in Svelte encapsulates its styles, which ensures that there are no clashes with global styles. Additionally, the Svelte compiler optimizes CSS styles by removing unused styles from your final bundle.

4. Reactive Statements

Svelte supports reactive statements, allowing you to create computed values that update whenever the dependencies change. You can achieve this using a unique syntax that leverages the dollar sign ($) before the colon in variable definitions.

Building a Fullstack Real-Time Todo Application

Now that we’re familiar with the fundamental concepts of Svelte 3, let’s dive into creating a real-time todo application using Svelte and Firebase.

Step 1: Set Up Your Svelte Project

You can quickly create a new Svelte project with the help of a template. Open your terminal and run:

npx degit sveltejs/template svelte-todo-app
cd svelte-todo-app
npm install
npm run dev

This initializes your Svelte application, and you should see your app running at localhost:5000.

Step 2: Project Structure and Firebase Setup

Create a new file named firebase.js to initialize Firebase. Ensure you have Firebase set up for your project. The file should look like this:

import { initializeApp } from "firebase/app";
import { getFirestore } from "firebase/firestore";

const firebaseConfig = {
  // your firebase config here
};

const app = initializeApp(firebaseConfig);
const db = getFirestore(app);

export { db };

Step 3: Create the Todo Component

Develop a component for your todos. The component will handle the display and maintain the state of each todo item. This is how the structure will look:

<script>
  export let todo;
  export let toggle;
  export let remove;
</script>

<div class="todo {{todo.complete ? 'completed' : ''}}">
  <span>{todo.text}</span>
  <button on:click={() => toggle(todo.id)}>Toggle</button>
  <button on:click={() => remove(todo.id)}>Remove</button>
</div>

Step 4: Manage Todos in the Main App

In your main App.svelte, you’ll handle the logic for creating, updating, and removing todos. Set up Firebase synchronization and manage the store like this:

<script>
  import { onMount } from "svelte";
  import { db } from './firebase.js';
  import Todo from './Todo.svelte';

  let todos = [];

  onMount(async () => {
    // Fetch todos from Firestore and update 'todos' array
  });

  const addTodo = async (text) => {
    // Add a new todo to Firestore
  };

  const toggleTodo = async (id) => {
    // Toggle complete status of the todo in Firestore
  };

  const removeTodo = async (id) => {
    // Remove todo from Firestore
  };
</script>

<input type="text" bind:value={newTodo} />
<button on:click={() => addTodo(newTodo)}>Add Todo</button>

{#each todos as todo (todo.id)}
  <Todo {todo} toggle={toggleTodo} remove={removeTodo}/>
{/each}

Step 5: Enhance the User Experience with Transitions

Svelte seamlessly integrates transitions for elements being added or removed from the DOM. You can animate transitions by adding the following code:

import { fade, fly } from "svelte/transition";

{#each todos as todo (todo.id)}
  <Todo {todo} toggle={toggleTodo} remove={removeTodo} in:fade out:fly={{ x: 200 }} />
{/each}

This enhances user interaction by providing visual cues during the item list modifications.

Conclusion

Svelte 3 introduces a paradigm shift in how developers approach front-end development. Its compiler-based architecture, combined with a highly reactive programming model, offers an efficient way to build interactive web applications. By exploring the process of creating a fullstack real-time todo application, we’ve highlighted the key strengths of Svelte, demonstrating how it can streamline your development workflow while providing an engaging user experience.

If you’re interested in diving into Svelte 3, I encourage you to try building your own projects using its features. The vibrant Svelte community is also a great resource to connect with other developers and share your experiences. Happy coding!