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Wes Bos

Wes Bos

XL5G3 Full Stack JavaScript Developer. Creator of really good web development courses. BBQ enthusiast.

Scott Tolinski

Scott Tolinski

Web Developer, NX2V1, Creator of Level Up Tuts, Bboy, Robotops Crew and Youtuber

Playing: 250: Scott Teaches Wes Svelte and Sapper



May 20th, 2020

Scott Teaches Wes Svelte and Sapper

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In this episode of Syntax, Scott teaches Wes about Svelte and Sapper — general premise, best practices, and more!

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Show Notes

03:14 - General premise

  • Sapper compiles away, removing framework code from build
  • Component & Props based
  • Easy reactivity
  • Built-in tools like animation
  • Template-based

07:57 - Svelte 101

  • .svelte files
  • Files can include <script>, <style>, and straight-up CSS
  • Variables are used in templates via {var} - <img {src} /> even works
  • Import component and use just like React and Vue

10:49 - Stylin'

  • All styles are scoped by default
  • global() to wrap around global declarations
  • Language type sass to use sass

12:22 - Reactivity

  • Baked in
    • let count = 0
    • count = count + 1 will reactively update in template
    • variables are essentially state
    • $: double = count + 2 - to create a reactive variable that updates when another variable updates
    • $: console.log(count) = will run whenever count is update a-la useEffect
    • $: if (count >10) = same... reactive if
    • <input bind:value={name} > updates let name in script

15:55 - Props

  • Same was React, but need to be exported before they can be used
  • Seems counterintuitive, but you get over it quickly
  • EZ defaults export let answer = 'a mystery';
import Nested from './Nested.svelte';

<Nested answer={42}/>
    export let answer = 'a mystery';

<p>The answer is {answer}</p>

20:08 - Template logic

  • If statements {#if user._id} {/if}

  • Loops {#each cats as kittens}

  • Promise tags

    {#await promise}
    {:then number}
      <p>The number is {number}</p>
    {:catch error}
      <p style="color: red">{error.message}</p>

23:12 - Events

  • <button on:click={func} />
  • On directive
  • Functions can also be inline
  • Modifiers
<button on:click|preventDefault={handleClick}>
    Click me

26:11 - Baked-in goodies

  • Animation
  • Dimensions
<div bind:clientWidth={w} bind:clientHeight={h}><span style="font-size: {size}px">{text}</span></div>
  • Lifecycle methods
  • Advanced State Via Stores
    • A store is simply an object with a subscribe method that allows interested parties to be notified whenever the store value changes.
  • import { writable } from 'svelte/store';
  • export const count = writable(0);
  • count.update(0)
  • Slots
  • React helmet like stuff, ie svelte:head

36:39 - Sapper

  • Similar to Next.js
  • Folder routes
  • Static export with all of the good stuff like service workers and preloading


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