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How to Build a Full-Stack Svelte Application Step-by-Step

22 September 2023

How to Build a Full-Stack Svelte Application Step-by-Step

Svelte.js has quickly become one of the most popular open-source JavaScript frameworks. This progressive framework stands out for its high performance and small bundle sizes. By converting components into highly optimized vanilla JavaScript at build time, Svelte achieves better performance than traditional frameworks that interpret code at runtime.

This article can be used as support material for our delegates who are on our Svelte.js training course the perfect opportunity to train for you or your team. To find out more please feel free to get in contact. 

In this comprehensive guide, you'll learn how to build a full-stack web application using Svelte from start to finish. We'll cover key concepts like components, routing, state management, and authentication. You'll gain hands-on experience setting up a Svelte development environment, building reusable components, integrating APIs, and deploying to production. Follow along to level up your Svelte skills!

An Introduction to Svelte

Before diving into building an app, let's start with an overview of Svelte itself.

Svelte is a component framework that runs in the browser rather than relying on a virtual DOM. During the build process, your Svelte components are converted into tiny, highly optimized vanilla JS modules. This results in faster rendering and smaller bundle sizes.

Some of the key benefits of using Svelte include:

  • Performance - Avoiding the overhead of a virtual DOM makes Svelte extremely fast. Apps are rendered efficiently with minimal code.
  • Size - Svelte outputs compact code, reducing the bundle size significantly compared to other frameworks.
  • Simplicity - Svelte has a relatively small API surface and is easy for developers to pick up.
  • Reactivity - The reactivity system automatically updates components when data changes. No need to manage state manually.

By learning Svelte, you can build incredibly fast web apps with excellent user experiences. It's one of the best frameworks for crafting high-performance frontend applications.

Prerequisites for Learning Svelte

To build apps with Svelte, you'll need a basic understanding of the following:

  • HTML - For structuring content on pages
  • CSS - For styling and layout
  • JavaScript - For component logic and functionality
  • Command line - For installing dependencies and running builds

You'll also want to have Node.js and npm installed locally. Optionally, an IDE like VS Code will be helpful for editing code.

With those basics covered, you're ready to start using Svelte to develop web applications. We'll explain other concepts along the way.

Setting Up a Svelte Development Environment

Let's get your environment configured for developing with Svelte. We'll install Svelte globally, generate a new project, examine the directory structure, install dependencies, and start up a dev server.

Installing Svelte Globally

We first need the Svelte CLI, which is available as an npm package. Open up your terminal and enter:

  npm install -g svelte  

This installs the svelte command globally, allowing you to generate new projects and compile Svelte code from the command line.

Creating a New Svelte Project

Use the svelte command to generate a new project skeleton:

  svelte new my-svelte-app  

This creates a my-svelte-app directory with starter code for an app. Navigate into this directory to continue setting up your environment.

Project Directory Structure

The generated app contains the following key files and directories:

  • public/ - Static assets like index.html and global styles
  • src/ - Svelte component files
  • rollup.config.js - Module bundler configuration
  • package.json - Dependencies and scripts

This gives you a standard project layout optimized for Svelte.

Installing Project Dependencies

Svelte apps rely on a few core packages to add functionality like routing and state management. Install these by running:

  npm install  

The key Svelte-related dependencies added are:

  • svelte - Svelte compiler
  • svelte-preprocess - For preprocessing Svelte files
  • @sveltejs/adapter-static - Static site generator adapter
  • @sveltejs/kit - SvelteKit for routing and endpoints
  • @sveltejs/adapter-node - Server-side rendering adapter

Starting the Development Server

Finally, start up the local dev server with:

  npm run dev  

This compiles your app and serves it at http://localhost:5000. Visiting this URL will display your running Svelte app, which you can now develop further.

With your environment set up, you're ready to build your first Svelte components!

Creating Reusable Svelte Components

Components are the building blocks of Svelte apps. Let's explore how to create and use Svelte components.

A component is a reusable self-contained module, similar to a JavaScript function. To define one, create a .svelte file like:

  <!-- src/Hello.svelte --> <script> // logic goes here </script> <h1>Hello World!</h1> <style> /* styles go here */ </style>  

This single file contains the component markup, logic, and styles. You can import it anywhere in your app.

Component Syntax

Svelte introduces some unique shortcuts for declaring components:

  • <script> - For JavaScript logic and importing other modules
  • <style> - For scoped component CSS
  • {expressions} - Insert values into markup
  • on:event - Declare event handlers
  • bind:prop - Bind to component props
  • $store - Access store values

These features streamline building encapsulated components.

Creating a Reusable Button

Let's build a reusable <Button> component:

  <!-- src/Button.svelte --> <script> export let text; function handleClick() { alert('Button clicked!'); } </script> <button on:click={handleClick}> {text} </button> <style> /* button styles */ </style>  

We can import this anywhere and customize the text prop:

  <script> import Button from './Button.svelte'; </script> <Button text="Subscribe" />  

This separates our presentation logic into reusable pieces.

Component Lifecycle

Svelte components fire events on creation, update, and destruction:

  • onMount - When component is created
  • beforeUpdate - Before component updates
  • afterUpdate - After component updates
  • onDestroy - When component is removed

For example, to run logic when a component mounts:

  <script> import { onMount } from 'svelte'; onMount(() => { console.log('Component mounted!'); }); </script>  

Use lifecycle events to integrate with external logic and libraries.

Now you know how to build encapsulated, reusable components - the core of Svelte apps!

Implementing Routing in a Svelte App

Let's explore how to handle navigation and routing in a Svelte application. We'll use the SvelteKit framework for setting up routes and endpoints.

Routing allows you to:

  • Create navigation between pages
  • Map components to URL paths
  • Pass parameters via the URL
  • Load data on route changes

Install SvelteKit

Add SvelteKit to your project with:

  npm install -D @sveltejs/kit  

This provides functions for routing, server endpoints, and more.

Pages and Routes

SvelteKit uses the src/routes directory to define routes. Each .svelte file becomes a webpage route:

  src/routes/ - index.svelte -> '/' - about.svelte -> '/about' - blog/[slug].svelte -> '/blog/:slug'  

Navigate between pages by importing page from SvelteKit and pushing new routes.

Dynamic Routes and Params

Routes like blog/[slug].svelte with brackets create dynamic routes that accept parameters.

Access the params in the component with url.params:

  <!-- blog/[slug].svelte --> <h1>{url.params.slug}</h1>  

This allows building routes like /blog/hello-world.

Navigation Functions

Use the goto function to navigate pages:

  <script> import { goto } from '@sveltejs/kit'; function goToAbout() { goto('/about'); } </script>  

SvelteKit provides functions like goto, preload, fetch and more to control navigation.

With SvelteKit integrated, you can build multi-page app workflows with ease!

Implementing State Management

For managing data throughout components, Svelte provides built-in state management with stores. Let's see how we can use stores to share state.

Creating a Store

Stores contain values that can update reactively. Define stores by importing writable from 'svelte/store':

  // store.js import { writable } from 'svelte/store'; export const count = writable(0);  

This creates a store named count with an initial value of 0.

Subscribing to Store Changes

In Svelte components, import the store and use the $ prefix to access its value:

  <script> import { count } from './store.js'; </script> <h1>Count: {$count}</h1>  

Svelte will automatically re-render the component when the store value changes.

Updating Store Values

To modify stores, access its set and update methods:

  count.update(n => n + 1); // Increment count  

This allows sharing state between components reactively using stores.

Adding User Authentication

Let's explore how to implement user authentication in a Svelte app, including login, protected routes, and managing state.

For authentication, we'll use an external library like svelte-auth.

Install the Auth Library

Add svelte-auth with:

  npm install svelte-auth  

Then import it in your app.

Login and Logout

Call authenticate and logout to sign users in and out:

  import { authenticate, logout } from 'svelte-auth'; authenticate('credentials'); // logs user in logout(); // logs user out  

Store the user data in a writable store on login.

Protecting Routes

Wrap routes in the Authenticated component to check auth:

  <Authenticated> <Route path="/settings" component={Settings}/> </Authenticated>  

This redirects unauthorized users.

Updating UI and Data

When the auth state changes:

  • Update the user store with the new data
  • Toggle UI elements depending on auth state

This allows you to add full user authentication flows to your Svelte apps!

Building and Deploying a Svelte Application

Let's explore how to build a production-ready Svelte application and deploy it for others to use.

Preparing for Production

For production builds, Svelte provides the svelte-kit build command. This:

  • Minifies and optimizes your code
  • Prerenders static pages where possible
  • Generates service workers for offline support

Set import.meta.env.MODE to production

Exporting the Built App

Run the production build with:

  svelte-kit build  

This outputs an optimized version of your app in build/.

Deployment Options

There are a few options for deploying your app:

  • Static Hosting - Upload the build/ folder to a platform like Vercel or Netlify
  • Node Server - Run a Node server that serves the built app
  • Docker Container - Package the app in a Docker container to deploy anywhere

Choose whichever hosting method best suits your stack and needs!

With that, you're ready to ship your Svelte creation to the world!

Key Takeaways and Next Steps

Congratulations, you've built an entire full-stack web application with Svelte!

Here are some key takeaways:

  • Svelte is a blazing fast compiler-based JavaScript framework
  • Components, routing, state stores handle much of the core app functionality
  • SvelteKit provides routing, endpoints, and server-rendering
  • Apps can be built for production and deployed to various platforms

To continue learning Svelte:

  • Build more complex components with advanced features
  • Integrate Svelte with external data sources
  • Explore animations, transitions, and reactive statements
  • Check out other Svelte add-ons like Svelte Testing Library

Svelte makes it easy to build super fast web apps. Now put your skills to work on your own Svelte projects!

Frequently Asked Questions

Here are answers to some common questions about Svelte development:

How does Svelte compare to React or Vue?

Svelte has performance advantages because it compiles away abstraction layers like the virtual DOM. It also includes features like reactivity out of the box. However, React and Vue have larger ecosystems currently.

Can I use TypeScript with Svelte?

Yes, Svelte fully supports TypeScript for those who prefer typed languages. Just rename files to .svelte.ts.

Does Svelte work with frontend frameworks like Tailwind CSS?

Absolutely! You can incorporate any CSS framework into Svelte projects and use those styles within your components.

Can I make mobile apps with Svelte?

Svelte Native allows you to build mobile apps for iOS and Android using Svelte. There are also tools for building mobile web apps with Svelte.

Is Svelte good for big enterprise applications?

Svelte's great performance along with capabilities like code splitting make it well-suited for large, complex enterprise apps and internal business tools.

And there you have it - a comprehensive guide to building full-stack apps with Svelte step-by-step!

As mentioned at the start of the article JBI Training offers a fully comprehensive course in Svelte.js part of our resources include blog articles and how to guides including our previous article Getting Started with Svelte.js: A Beginner's Guide

or consider one of our other training courses. 

Here are some other JBI Training courses that relate to building full-stack Svelte applications:

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