How to Build a Svelte Frontend and Connect It to a Backend?

in this tutorial, you’ll build a to do list application using svelte and connect it to a managed backend service powered by back4app this guide is designed for you if you want to master essential crud (create, read, update, delete) operations and create an intuitive interface using svelte by the end, your application will interact seamlessly with a backend that handles data storage, authentication, and more developing a full stack application can be complex due to backend configuration and database management to simplify your work, we use back4app—a robust backend as a service —so you can focus on building a dynamic svelte frontend back4app provides a fully managed nosql database, authentication, cloud code for custom logic, and sdks for smooth integration this enables you to deploy scalable applications without managing server infrastructure key takeaways by following this tutorial, you will initialize a modern svelte project with vite seamlessly integrate a backend service to manage your app’s data implement essential crud operations for a dynamic to do list deploy your fully functional application using containerized workflows on back4app prerequisites before you begin, make sure you have node js and npm installed on your machine verify with node v and npm v basic svelte knowledge , including components, reactive variables, and event handling a back4app account to manage your backend services sign up at back4app https //www back4app com/ if you don’t already have one with these prerequisites in place, you’re ready to start building your project project setup begin by setting up your local development environment and initializing a new svelte project using vite ensure you have node js (lts version) installed if not, download it from nodejs org https //nodejs org/ create your svelte project by running npm create vite\@latest todo app template svelte change to your project directory cd todo app install the necessary dependencies npm install start the development server to verify the setup npm run dev open the provided url in your browser to see your svelte app in action with the frontend ready, proceed to create your backend on back4app creating the todo backend back4app offers a fully managed backend service powered by parse it includes a nosql database, authentication, cloud code, and auto generated apis follow these steps to set up your backend log in to your back4app dashboard https //www back4app com/ and click "create a new app " name your app (for example, todoapp ) and select nodejs/parse as the backend type navigate to "database" > "browser" , click "create a class" , and choose "custom" name the class task and set permissions to allow public read and write (you can refine these later) in the task class, add the following fields title (string) – the title of the task description (string) – details about the task completed (boolean) – task completion status duedate (date) – the deadline for the task click "save" to create the schema integrating back4app with svelte to connect your svelte app with back4app, you will use the parse javascript sdk install the parse sdk npm install parse configure the sdk by editing the src/main js file import the sdk and initialize it with your application id and javascript key from the back4app dashboard (find these under app settings > security & keys ) import app from ' /app svelte'; import parse from 'parse/dist/parse min js'; const parse app id = 'your application id'; const parse js key = 'your javascript key'; const parse server url = 'https //parseapi back4app com/'; parse initialize(parse app id, parse js key); parse serverurl = parse server url; const app = new app({ target document getelementbyid('app') }); export default app; with your backend connected, you can now build the to do list interface and implement crud operations developing the frontend your svelte application will consist of components that let you add, display, update, and delete tasks you will leverage svelte’s reactivity for dynamic updates structuring your components create a components folder inside src to organize your svelte components mkdir src/components you will create the following components taskform svelte – for adding new tasks tasklist svelte – to display the list of tasks taskitem svelte – to represent individual tasks taskform svelte this component renders a form that captures task details and submits them to back4app \<script> import { createeventdispatcher } from 'svelte'; import parse from 'parse/dist/parse min js'; let title = ''; let description = ''; const dispatch = createeventdispatcher(); async function handlesubmit(event) { event preventdefault(); try { const task = parse object extend('task'); const task = new task(); task set('title', title); task set('description', description); task set('completed', false); await task save(); dispatch('refresh'); title = ''; description = ''; } catch (error) { console error('error adding task ', error); } } \</script> \<form on\ submit|preventdefault={handlesubmit}> \<input type="text" placeholder="task title" bind\ value={title} required /> \<input type="text" placeholder="description" bind\ value={description} required /> \<button type="submit">add task\</button> \</form> taskitem svelte this component represents an individual task, allowing you to toggle its completion status or delete it \<script> import parse from 'parse/dist/parse min js'; export let task; export let refresh; async function togglecomplete() { try { const query = new parse query('task'); const tasktoupdate = await query get(task id); tasktoupdate set('completed', !task completed); await tasktoupdate save(); refresh(); } catch (error) { console error('error updating task ', error); } } async function deletetask() { try { const query = new parse query('task'); const tasktodelete = await query get(task id); await tasktodelete destroy(); refresh(); } catch (error) { console error('error deleting task ', error); } } \</script> \<div class="task item {task completed ? 'completed' ''}"> \<div> \<h3>{task title}\</h3> \<p>{task description}\</p> \</div> \<div> \<button on\ click={togglecomplete}> {task completed ? 'undo' 'complete'} \</button> \<button on\ click={deletetask}>delete\</button> \</div> \</div> tasklist svelte this component displays all tasks by iterating over them and rendering each using taskitem \<script> import taskitem from ' /taskitem svelte'; export let tasks = \[]; export let refresh; \</script> {#if tasks length === 0} \<p>no tasks available\</p> {\ else} {#each tasks as task (task id)} \<taskitem {task} {refresh} /> {/each} {/if} app svelte in your main component, manage the application state and integrate your task components \<script> import { onmount } from 'svelte'; import parse from 'parse/dist/parse min js'; import taskform from ' /components/taskform svelte'; import tasklist from ' /components/tasklist svelte'; let tasks = \[]; async function fetchtasks() { try { const task = parse object extend('task'); const query = new parse query(task); const results = await query find(); tasks = results map(task => ({ id task id, task tojson() })); } catch (error) { console error('error fetching tasks ', error); } } onmount(fetchtasks); \</script> \<div class="container"> \<h1>to do list\</h1> \<taskform on\ refresh={fetchtasks} /> \<tasklist {tasks} refresh={fetchtasks} /> \</div> styling the application create a src/global css file to add basic styling container { max width 600px; margin 40px auto; padding 0 20px; text align center; font family sans serif; } container h1 { margin bottom 20px; } form { display flex; flex direction column; align items center; gap 10px; margin bottom 20px; } form input\[type="text"] { width 80%; max width 400px; padding 8px; box sizing border box; font size 1rem; } form button { padding 8px 16px; cursor pointer; font size 1rem; border none; background color #eaeaea; transition background color 0 2s ease; } form button\ hover { background color #ccc; } task item { display flex; flex direction column; align items center; justify content center; gap 12px; border 1px solid #ccc; border radius 6px; padding 15px; margin 10px 0; background color #fafafa; text align center; transition background color 0 2s ease; } task item completed h3, task item completed p { text decoration line through; color #888; } task item h3 { margin 0; font size 1 1rem; } task item p { margin 0; font size 1rem; } task item button { padding 6px 12px; border none; background color #eaeaea; cursor pointer; font size 0 9rem; } task item button\ hover { background color #ccc; } @media (min width 600px) { task item { flex direction row; } } import this stylesheet in your src/main js import ' /global css'; deploying the frontend on back4app web deployment back4app web deployment offers a containerized environment to host your svelte application configuring vite for production adjust vite config js if necessary to set the base path correctly for a containerized environment import { defineconfig } from 'vite'; import { svelte } from '@sveltejs/vite plugin svelte'; export default defineconfig({ plugins \[svelte()], base ' /', }); generate the production build npm run build creating a dockerfile create a dockerfile in the root directory with the following content \# stage 1 build the svelte app from node 18 alpine as build workdir /app copy package json package lock json / run npm install copy run npm run build \# stage 2 serve the app using nginx from nginx\ alpine copy from=build /app/dist /usr/share/nginx/html expose 80 cmd \["nginx", " g", "daemon off;"] testing the docker container locally build your docker image docker build t todo frontend run the container docker run p 8080 80 todo frontend open http //localhost 8080 in your browser to verify that your svelte app is served correctly deploying to back4app initialize a git repository, add your project files, and commit git init git add git commit m "initial commit for back4app deployment" git branch m main git remote add origin \<your github repository url> git push u origin main log in to back4app web deployment https //www back4app com/containers click "create new app" , provide your project name, and select your github repository authorize back4app and choose dockerfile deployment confirm the build settings and click "deploy" to initiate the first build monitoring your deployment after deployment, use the back4app dashboard to view logs for debugging monitor container performance and resource usage trigger rebuilds on new commits configure custom domains if needed access your live application at https //todoapp ku5ofg8s b4a run/ https //todoapp ku5ofg8s b4a run/ https //todoapp ku5ofg8s b4a run/ testing and debugging after deployment, confirm that your svelte frontend properly communicates with the back4app backend api verification use your browser’s developer tools (f12 → network) to inspect api calls task operations add, complete, and delete tasks via the ui and verify the updates in the back4app database browser error handling check console logs for errors and test edge cases such as submitting empty tasks performance testing simulate slow network conditions using browser tools to assess responsiveness best practices for using back4app with svelte to optimize your application efficient requests use batch operations when handling multiple tasks const tasks = \[task1, task2, task3]; parse object saveall(tasks); optimized queries retrieve only the necessary fields query select('title', 'completed'); environment variables store sensitive keys in a env file vite parse app id=your app id vite parse js key=your js key security use acls to restrict access task setacl(new parse acl(parse user current())); backend offloading leverage cloud code for complex business logic to reduce api exposure conclusion you have now built a full stack to do list application by creating a svelte frontend, integrating it with back4app’s backend, and deploying it using containerized workflows this tutorial walked you through every step—from local development to cloud deployment—ensuring smooth interaction between your svelte ui and backend services looking ahead, consider enhancing your app with real time updates, improved authentication, and third party integrations for further learning, visit the back4app documentation https //www back4app com/docs and explore community resources