Svelte 5 vs Marko comparison

<script>
  let name = $state("John");
</script>

<h1>Hello {name}</h1>

<let/name = "John"/>
<h1>Hello ${name}</h1>

<script>
  let name = $state("John");
  name = "Jane";
</script>

<h1>Hello {name}</h1>

<let/name = "John"/>
<effect() { name = "Jane" }/>
<h1>Hello ${name}</h1>

<script>
  let count = $state(10);
  const doubleCount = $derived(count * 2);
</script>

<div>{doubleCount}</div>

<let/count = 10/>
<const/doubleCount = count * 2/>
<div>${doubleCount}</div>

<h1>Hello world</h1>

<h1>Hello world</h1>

<h1 class="title">I am red</h1>
<button style="font-size: 10rem;">I am a button</button>

<style>
  .title {
    color: red;
  }
</style>

<h1.title>I am red</h1>
<button style={ fontSize: "10rem" }>I am a button</button>
<button class=scopedButton>I am a style-scoped button</button>

<style>
  .title {
    color: red;
  }
</style>
<style/{ scopedButton }>
  .scopedButton {
    font-size: 10rem;
  }
</style>

<script>
  const colors = ["red", "green", "blue"];
</script>

<ul>
  {#each colors as color (color)}
    <li>{color}</li>
  {/each}
</ul>

<ul>
  <for|color| of=["red", "green", "blue"]>
    <li>${color}</li>
  </for>
</ul>

<script>
  let count = $state(0);

  function incrementCount() {
    count++;
  }
</script>

<p>Counter: {count}</p>
<button onclick={incrementCount}>+1</button>

<let/count = 0/>
<p>Counter: ${count}</p>
<button onClick() { count++ }>+1</button>

<script>
  let inputElement;

  $effect(() => {
    inputElement.focus();
  });
</script>

<input bind:this={inputElement} />

<input/inputElement>
<effect() { inputElement().focus() }/>

<script>
  const TRAFFIC_LIGHTS = ["red", "orange", "green"];
  let lightIndex = $state(0);

  const light = $derived(TRAFFIC_LIGHTS[lightIndex]);

  function nextLight() {
    lightIndex = (lightIndex + 1) % TRAFFIC_LIGHTS.length;
  }
</script>

<button onclick={nextLight}>Next light</button>
<p>Light is: {light}</p>
<p>
  You must
  {#if light === "red"}
    <span>STOP</span>
  {:else if light === "orange"}
    <span>SLOW DOWN</span>
  {:else if light === "green"}
    <span>GO</span>
  {/if}
</p>

static const TRAFFIC_LIGHTS = ["red", "orange", "green"];
<let/lightIndex = 0/>
<const/light = TRAFFIC_LIGHTS[lightIndex]/>

<button onClick() { lightIndex = (lightIndex + 1) % TRAFFIC_LIGHTS.length }>
  Next light
</button>
<p>Light is: ${light}</p>
<p>
  You must
  <if=light === "red">STOP</if>
  <else-if=light === "orange">SLOW DOWN</else-if>
  <else>GO</else>
</p>

<script>
  let pageTitle = $state("");
  $effect(() => {
    pageTitle = document.title;
  });
</script>

<p>Page title: {pageTitle}</p>

<let/pageTitle = ""/>
<effect() { pageTitle = document.title }/>
<p>Page title: ${pageTitle}</p>

<script>
  let time = $state(new Date().toLocaleTimeString());

  $effect(() => {
    const timer = setInterval(() => {
      time = new Date().toLocaleTimeString();
    }, 1000);

    return () => clearInterval(timer);
  });
</script>

<p>Current time: {time}</p>

<let/time = new Date()/>
<lifecycle
  onMount() { this.timer = setInterval(_ => time = new Date(), 1000) }
  onDestroy() { clearInterval(this.timer) }
/>
<p>Current time: ${time.toLocaleTimeString()}</p>

<script>
  import UserProfile from "./UserProfile.svelte";
</script>

<UserProfile
  name="John"
  age={20}
  favouriteColors={["green", "blue", "red"]}
  isAvailable
/>

<UserProfile
  name="John"
  age=20
  favouriteColors=["green", "blue", "red"]
  isAvailable
/>

<script>
  import AnswerButton from "./AnswerButton.svelte";

  let isHappy = $state(true);

  function onAnswerNo() {
    isHappy = false;
  }

  function onAnswerYes() {
    isHappy = true;
  }
</script>

<p>Are you happy?</p>
<AnswerButton onYes={onAnswerYes} onNo={onAnswerNo} />
<p style="font-size: 50px;">{isHappy ? "😀" : "😥"}</p>

<let/isHappy = true/>
<p>Are you happy?</p>
<AnswerButton
  onYes() { isHappy = true }
  onNo() { isHappy = false }
/>
<p style={ fontSize: 50 }>${isHappy ? "😀" : "😥"}</p>

<script>
  import FunnyButton from "./FunnyButton.svelte";
</script>

<FunnyButton>Click me!</FunnyButton>

<FunnyButton>Click me!</FunnyButton>

<script>
  import FunnyButton from "./FunnyButton.svelte";
</script>

<FunnyButton />
<FunnyButton>I got content!</FunnyButton>

<FunnyButton/>
<FunnyButton>I got content!</FunnyButton>

<script>
  import { setContext } from "svelte";
  import UserProfile from "./UserProfile.svelte";
  import createUserState from "./createUserState.svelte.js";

  const user = createUserState({
    id: 1,
    username: "unicorn42",
    email: "unicorn42@example.com",
  });

  setContext("user", user);
</script>

<h1>Welcome back, {user.username}</h1>
<UserProfile />

<let/user = {
  id: 1,
  username: "unicorn42",
  email: "unicorn42@example.com",
}/>
<const/updateUsername(newUsername) {
  user = { ...user, username: newUsername };
}/>

<h1>Welcome back, ${user.username}</h1>
<set={ ...user, updateUsername }>
  <UserProfile />
</set>

<script>
  let text = $state("Hello World");
</script>

<p>{text}</p>
<input bind:value={text} />

<let/text = "Hello world"/>
<p>${text}</p>
<input value:=text/>

<script>
  let isAvailable = $state(false);
</script>

<input id="is-available" type="checkbox" bind:checked={isAvailable} />
<label for="is-available">Is available</label>

<input#is-available
  type="checkbox"
  checked:=input.isAvailable
/>
<label for="is-available">Is available</label>

<script>
  let picked = $state("red");
</script>

<div>Picked: {picked}</div>

<input id="blue-pill" bind:group={picked} type="radio" value="blue" />
<label for="blue-pill">Blue pill</label>

<input id="red-pill" bind:group={picked} type="radio" value="red" />
<label for="red-pill">Red pill</label>

<let/picked = "red"/>
<const/handleChange(event) {
  picked = event.target.value;
}/>

<div>Picked: ${picked}</div>
<input#blue-pill
  type="radio"
  checked=picked === "blue"
  value="blue"
  onChange=handleChange
/>
<label for="blue-pill">Blue pill</label>

<input#red-pill
  type="radio"
  checked=picked === "red"
  value="red"
  onChange=handleChange
/>
<label for="red-pill">Red pill</label>

<script>
  let selectedColorId = $state(2);

  const colors = [
    { id: 1, text: "red" },
    { id: 2, text: "blue" },
    { id: 3, text: "green" },
    { id: 4, text: "gray", isDisabled: true },
  ];
</script>

<select bind:value={selectedColorId}>
  {#each colors as color}
    <option value={color.id} disabled={color.isDisabled}>
      {color.text}
    </option>
  {/each}
</select>

static const colors = [
  { id: 1, text: "red" },
  { id: 2, text: "blue" },
  { id: 3, text: "green" },
  { id: 4, text: "gray", isDisabled: true },
];
<let/selectedColorId = 2/>

<select onChange(event) { selectedColorId = event.target.value }>
  <for|{ id, isDisabled, text }| of=colors>
    <option value=id disabled=isDisabled selected=id === selectedColorId>
      ${text}
    </option>
  </for>
</select>

<!DOCTYPE html>
<html>
  <body>
    <div id="app"></div>
    <script type="module" src="./app.js"></script>
  </body>
</html>

<!DOCTYPE html>
<html>
  <App/>
</html>

<script>
  import useFetchUsers from "./useFetchUsers.svelte.js";

  const response = useFetchUsers();
</script>

{#if response.isLoading}
  <p>Fetching users...</p>
{:else if response.error}
  <p>An error occurred while fetching users</p>
{:else if response.users}
  <ul>
    {#each response.users as user}
      <li>
        <img src={user.picture.thumbnail} alt="user" />
        <p>
          {user.name.first}
          {user.name.last}
        </p>
      </li>
    {/each}
  </ul>
{/if}

<await(fetch("https://randomuser.me/api/?results=3").then(res => res.json()))>
  <@placeholder>
    <p>Fetching users...</p>
  </@placeholder>
  <@catch|error|>
    <p>An error occurred while fetching users</p>
  </@catch>
  <@then|{ results: users }|>
    <ul>
      <for|{ picture, name }| of=users>
        <li>
          <img src=picture.thumbnail alt="user">
          <p>${name.first} ${name.last}</p>
        </li>
      </for>
    </ul>
  </@then>
</await>