Reactive values just define a value wthin the script tag and start using it anwhere in the main section of the app prefix on defination with $:

example

<script>
    let firstName="Raptors";
    let lastName="Beak"
    let color='blue'
    let showText=false
    // reactive value
    $: name=firstName+' '+lastName
</script>

<main>
// Consume the reactive value and if either firstName or lastName changes then name will aslo change
{name}
</main>

Event binding on:

inline handler or pass reference to a function that will be called on the event

on:eventType

<script>
    let color='red'
    const toggleColor=()=>{
        color=color==='red'?'blue':'red'
    }
</script>

<main>
    <button on:click={()=>{
        color=color==='red'?'blue':'red'
    }}>Inline</button>
    <button on:click="toggleColor">HandleFunc</button>
</main>

Conditionals

{#if condition}
  {:else}
{/if}

example
{#if showText}
    <p>Visit the <a href="https://svelte.dev/tutorial">Svelte tutorial</a> to learn how to build Svelte apps.</p>
{:else}
    <p>Will add stuff on toggles</p>
{/if}

Looping constructs an array usrs each with a name and an id note the key is the (user.id) construct <!-- Looping --> {#each users as user (user.id)} <h3>{user.id} : {user.name}</h3> {/each}

All in all so far for the basics

<script>
    let firstName="Raptors";
    let lastName="Beak"
    let color='blue'
    let showText=false
    // reactive value
    $: name=firstName+' '+lastName
    // Involed in the onclick button
    const toggle=()=>{
        color=color==="blue"?'red':'blue'
        showText=!showText
        addUsers()
    }
    let users=[
        {id:'1',name:'John'},{id:'2',name:'Jacob'},{name:'Hans',id:3}
    ]
    const addUsers=()=>{
        let randId=Math.random(12)
        users=[...users,{id:randId,name:'Jane'}]
    }
</script>

<main>
    <h1 style="color: {color}"
    >Hello {name}!</h1>
    {#if showText}
        <p>Visit the <a href="https://svelte.dev/tutorial">Svelte tutorial</a> to learn how to build Svelte apps.</p>
    {:else}
        <p>Will add stuff on toggles</p>
    {/if}
    <!-- Events -->
    <!-- Inline -->
    <button on:click={()=>color="purple"}>Click Me</button>
    <!-- Named funcion -->
    <button on:click={toggle}>Toggle</button>

    <!-- Looping -->
    {#each users as user (user.id)}
        <h3>{user.id} : {user.name}</h3>
    {/each}
</main>

<style>
    main {
        text-align: center;
        padding: 1em;
        max-width: 240px;
        margin: 0 auto;
    }

    h1 {
        color: #ff3e00;
        text-transform: uppercase;
        font-size: 4em;
        font-weight: 100;
    }

    @media (min-width: 640px) {
        main {
            max-width: none;
        }
    }
</style>

Psst — looking for a more complete solution? Check out SvelteKit, the official framework for building web applications of all sizes, with a beautiful development experience and flexible filesystem-based routing.

Looking for a shareable component template instead? You can use SvelteKit for that as well or the older sveltejs/component-template

svelte app

This is a project template for Svelte apps. It lives at https://github.com/sveltejs/template.

To create a new project based on this template using degit:

npx degit sveltejs/template svelte-app
cd svelte-app

Note that you will need to have Node.js installed.

Get started

Install the dependencies...

cd svelte-app
npm install

...then start Rollup:

npm run dev

Navigate to localhost:5000. You should see your app running. Edit a component file in src, save it, and reload the page to see your changes.

By default, the server will only respond to requests from localhost. To allow connections from other computers, edit the sirv commands in package.json to include the option --host 0.0.0.0.

If you're using Visual Studio Code we recommend installing the official extension Svelte for VS Code. If you are using other editors you may need to install a plugin in order to get syntax highlighting and intellisense.

Building and running in production mode

To create an optimised version of the app:

npm run build

You can run the newly built app with npm run start. This uses sirv, which is included in your package.json's dependencies so that the app will work when you deploy to platforms like Heroku.

Single-page app mode

By default, sirv will only respond to requests that match files in public. This is to maximise compatibility with static fileservers, allowing you to deploy your app anywhere.

If you're building a single-page app (SPA) with multiple routes, sirv needs to be able to respond to requests for any path. You can make it so by editing the "start" command in package.json:

"start": "sirv public --single"

Using TypeScript

This template comes with a script to set up a TypeScript development environment, you can run it immediately after cloning the template with:

node scripts/setupTypeScript.js

Or remove the script via:

rm scripts/setupTypeScript.js

If you want to use baseUrl or path aliases within your tsconfig, you need to set up @rollup/plugin-alias to tell Rollup to resolve the aliases. For more info, see this StackOverflow question.

Deploying to the web

With Vercel

Install vercel if you haven't already:

npm install -g vercel

Then, from within your project folder:

cd public
vercel deploy --name my-project

With surge

Install surge if you haven't already:

npm install -g surge

Then, from within your project folder:

npm run build
surge public my-project.surge.sh