Svelte 4 vs Marko - JavaScript 框架语法对比

响应式

声明状态

Svelte 4

<script>
  let name = "张三";
</script>

<h1>你好 {name}</h1>

Marko

<let/name="张三">
<h1>你好 ${name}</h1>

更新状态

Svelte 4

<script>
  let name = "张三";
  name = "李四";
</script>

<h1>你好 {name}</h1>

Marko

<let/name="张三">
<script>name = "李四"</script>
<h1>你好 ${name}</h1>

计算属性

Svelte 4

<script>
  let count = 10;
  $: doubleCount = count * 2;
</script>

<div>{doubleCount}</div>

Marko

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

模板语法

最简模板

Svelte 4

<h1>你好，世界</h1>

Marko

<h1>你好，世界</h1>

样式

Svelte 4

<h1 class="title">我是红色的</h1>
<button style="font-size: 10rem;">我是一个按钮</button>

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

Marko

<h1.title>我是红色的</h1>
<button style={ "font-size": "10rem" }>我是一个按钮</button>
<button class=scopedButton>我是一个样式作用域按钮</button>

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

DOM循环

Svelte 4

<script>
  const colors = ["红", "绿", "蓝"];
</script>

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

Marko

<ul>
  <for|color| of=["红", "绿", "蓝"]>
    <li>${color}</li>
  </for>
</ul>

点击事件

Svelte 4

<script>
  let count = 0;

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

<p>计数器: {count}</p>
<button on:click={incrementCount}>+1</button>

Marko

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

DOM引用

Svelte 4

<script>
  import { onMount } from "svelte";

  let inputElement;

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

<input bind:this={inputElement} />

Marko

<input/inputElement>
<script>
  inputElement().focus();
</script>

条件渲染

Svelte 4

<script>
  const TRAFFIC_LIGHTS = ["红灯", "黄灯", "绿灯"];
  let lightIndex = 0;

  $: light = TRAFFIC_LIGHTS[lightIndex];

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

<button on:click={nextLight}>下一个灯</button>
<p>现在亮着的是: {light}</p>
<p>
  你应该
  {#if light === "红灯"}
    <span>停下</span>
  {:else if light === "黄灯"}
    <span>慢行</span>
  {:else if light === "绿灯"}
    <span>赶紧走</span>
  {/if}
</p>

Marko

static const TRAFFIC_LIGHTS = ["红灯", "黄灯", "绿灯"];
<let/lightIndex=0>
<const/light=TRAFFIC_LIGHTS[lightIndex]>

<button onClick() { lightIndex = (lightIndex + 1) % TRAFFIC_LIGHTS.length }>
  下一个灯
</button>
<p>现在亮着的是: ${light}</p>
<p>
  你应该
  <if=light === "红灯">停下</if>
  <else if=light === "黄灯">慢行</else>
  <else>赶紧走</else>
</p>

生命周期

组件加载时

Svelte 4

<script>
  import { onMount } from "svelte";
  let pageTitle = "";
  onMount(() => {
    pageTitle = document.title;
  });
</script>

<p>页面标题: {pageTitle}</p>

Marko

<let/pageTitle="">
<script>pageTitle = document.title</script>
<p>页面标题: ${pageTitle}</p>

组件卸载时

Svelte 4

<script>
  import { onDestroy } from "svelte";

  let time = new Date().toLocaleTimeString();

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

  onDestroy(() => clearInterval(timer));
</script>

<p>当前时间: {time}</p>

Marko

<let/time=new Date()>
<script>
  const id = setInterval(() => time = new Date(), 1000);
  $signal.onabort = () => clearInterval(id)
</script>
<p>当前时间: ${time.toLocaleTimeString()}</p>

组件组合

组件Props传参

Svelte 4

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

<UserProfile
  name="张三"
  age={20}
  favouriteColors={["green", "blue", "red"]}
  isAvailable
/>

Marko

<UserProfile
  name="张三"
  age=20
  favouriteColors=["green", "blue", "red"]
  isAvailable
/>

向父组件emit事件

Svelte 4

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

  let isHappy = true;

  function onAnswerNo() {
    isHappy = false;
  }

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

<p>你快乐吗?</p>
<AnswerButton on:yes={onAnswerYes} on:no={onAnswerNo} />
<p style="font-size: 50px;">{isHappy ? "😀" : "😥"}</p>

Marko

<let/isHappy=true>
<p>你快乐吗?</p>
<AnswerButton
  onYes() { isHappy = true }
  onNo() { isHappy = false }
/>
<p style={ "font-size": 50 }>${isHappy ? "😀" : "😥"}</p>

slot插槽

Svelte 4

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

<FunnyButton>点我!</FunnyButton>

Marko

<FunnyButton>点我!</FunnyButton>

slot插槽内容

Svelte 4

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

<FunnyButton />
<FunnyButton>这是传到slot的内容!</FunnyButton>

Marko

<FunnyButton/>
<FunnyButton>这是传到slot的内容!</FunnyButton>

上下文

Svelte 4

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

  const userStore = createUserStore({
    id: 1,
    username: "abcdefg",
    email: "[email protected]",
  });

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

<h1>欢迎回来, {$userStore.username}</h1>
<UserProfile />

Marko

<let/user={
  id: 1,
  username: "abcdefg",
  email: "[email protected]",
}>
<const/updateUsername(newUsername) {
  user = { ...user, username: newUsername };
}>

<h1>欢迎回来, ${user.username}</h1>
<context={ ...user, updateUsername }>
  <UserProfile />
</context>

表单输入

输入框

Svelte 4

<script>
  let text = "你好世界";
</script>

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

Marko

<let/text="你好世界">
<p>${text}</p>
<input value:=text>

复选框

Svelte 4

<script>
  let isAvailable = false;
</script>

<input id="is-available" type="checkbox" bind:checked={isAvailable} />
<label for="is-available">这是一个checkbox</label>

Marko

<input#is-available
  type="checkbox"
  checked:=input.isAvailable
>
<label for="is-available">这是一个checkbox</label>

单选框

Svelte 4

<script>
  let picked = "red";
</script>

<div>你选择了: {picked}</div>

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

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

Marko

<let/picked="red">

<div>你选择了: ${picked}</div>
<input#blue-pill
  type="radio"
  value="blue"
  checkedValue:=picked
>
<label for="blue-pill">蓝色</label>

<input#red-pill
  type="radio"
  value="red"
  checkedValue:=picked
>
<label for="red-pill">红色</label>

选择器

Svelte 4

<script>
  let selectedColorId = 2;

  const colors = [
    { id: 1, text: "红" },
    { id: 2, text: "蓝" },
    { id: 3, text: "绿" },
    { id: 4, text: "灰", isDisabled: true },
  ];
</script>

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

Marko

static const colors = [
  { id: 1, text: "红" },
  { id: 2, text: "蓝" },
  { id: 3, text: "绿" },
  { id: 4, text: "灰", isDisabled: true },
];
<let/selectedColorId=2>

<select value:=selectedColorId>
  <for|{ id, isDisabled, text }| of=colors>
    <option value=id disabled=isDisabled>
      ${text}
    </option>
  </for>
</select>

Web应用特性

渲染应用

Svelte 4

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

Marko

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

fetch获取数据

Svelte 4

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

  const { isLoading, error, data: users } = useFetchUsers();
</script>

{#if $isLoading}
  <p>正在获取用户信息……</p>
{:else if $error}
  <p>获取用户信息出错</p>
{:else if $users}
  <ul>
    {#each $users as user}
      <li>
        <img src={user.picture.thumbnail} alt="user" />
        <p>
          {user.name.first}
          {user.name.last}
        </p>
      </li>
    {/each}
  </ul>
{/if}

Marko

<try>
  <await|{ results: users }|=fetch("https://randomuser.me/api/?results=3").then(res => res.json())>
    <ul>
      <for|{ picture, name }| of=users>
        <li>
          <img src=picture.thumbnail alt="user">
          <p>${name.first} ${name.last}</p>
        </li>
      </for>
    </ul>
  </await>
  <@placeholder>
    <p>正在获取用户信息……</p>
  </@placeholder>
  <@catch|error|>
    <p>获取用户信息出错</p>
  </@catch>
</try>

响应式 #

声明状态 #

Svelte 4

Marko

更新状态 #

Svelte 4

Marko

计算属性 #

Svelte 4

Marko

模板语法 #

最简模板 #

Svelte 4

Marko

样式 #

Svelte 4

Marko

DOM循环 #

Svelte 4

Marko

点击事件 #

Svelte 4

Marko

DOM引用 #

Svelte 4

Marko

条件渲染 #

Svelte 4

Marko

生命周期 #

组件加载时 #

Svelte 4

Marko

组件卸载时 #

Svelte 4

Marko

组件组合 #

组件Props传参 #

Svelte 4

Marko

向父组件emit事件 #

Svelte 4

Marko

slot插槽 #

Svelte 4

Marko

slot插槽内容 #

Svelte 4

Marko

上下文 #

Svelte 4

Marko

表单输入 #

输入框 #

Svelte 4

Marko

复选框 #

Svelte 4

Marko

单选框 #

Svelte 4

Marko

选择器 #

Svelte 4

Marko

Web应用特性 #

渲染应用 #

Svelte 4

Marko

fetch获取数据 #

Svelte 4

Marko

响应式

声明状态

更新状态

计算属性

模板语法

最简模板

样式

DOM循环

点击事件

DOM引用

条件渲染

生命周期

组件加载时

组件卸载时

组件组合

组件Props传参

向父组件emit事件

slot插槽

slot插槽内容

上下文

表单输入

输入框

复选框

单选框

选择器

Web应用特性

渲染应用

fetch获取数据