Vue 3 vs Svelte 4 - JavaScript 框架语法对比

响应式

声明状态

Vue 3

<script setup>
import { ref } from "vue";
const name = ref("张三");
</script>

<template>
  <h1>你好 {{ name }}</h1>
</template>

Svelte 4

<script>
  let name = "张三";
</script>

<h1>你好 {name}</h1>

更新状态

Vue 3

<script setup>
import { ref } from "vue";
const name = ref("张三");
name.value = "李四";
</script>

<template>
  <h1>你好 {{ name }}</h1>
</template>

Svelte 4

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

<h1>你好 {name}</h1>

计算属性

Vue 3

<script setup>
import { ref, computed } from "vue";
const count = ref(10);
const doubleCount = computed(() => count.value * 2);
</script>

<template>
  <div>{{ doubleCount }}</div>
</template>

Svelte 4

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

<div>{doubleCount}</div>

模板语法

最简模板

Vue 3

<template>
  <h1>你好，世界</h1>
</template>

Svelte 4

<h1>你好，世界</h1>

样式

Vue 3

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

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

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>

DOM循环

Vue 3

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

<template>
  <ul>
    <li v-for="color in colors" :key="color">
      {{ color }}
    </li>
  </ul>
</template>

Svelte 4

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

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

点击事件

Vue 3

<script setup>
import { ref } from "vue";
const count = ref(0);

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

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

Svelte 4

<script>
  let count = 0;

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

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

DOM引用

Vue 3

<script setup>
import { useTemplateRef, onMounted } from "vue";

const inputElement = useTemplateRef("inputElement");

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

<template>
  <input ref="inputElement" />
</template>

Svelte 4

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

  let inputElement;

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

<input bind:this={inputElement} />

条件渲染

Vue 3

<script setup>
import { ref, computed } from "vue";
const TRAFFIC_LIGHTS = ["红灯", "黄灯", "绿灯"];
const lightIndex = ref(0);

const light = computed(() => TRAFFIC_LIGHTS[lightIndex.value]);

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

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

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>

生命周期

组件加载时

Vue 3

<script setup>
import { ref, onMounted } from "vue";
const pageTitle = ref("");
onMounted(() => {
  pageTitle.value = document.title;
});
</script>

<template>
  <p>页面标题: {{ pageTitle }}</p>
</template>

Svelte 4

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

<p>页面标题: {pageTitle}</p>

组件卸载时

Vue 3

<script setup>
import { ref, onUnmounted } from "vue";

const time = ref(new Date().toLocaleTimeString());

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

onUnmounted(() => {
  clearInterval(timer);
});
</script>

<template>
  <p>当前时间: {{ time }}</p>
</template>

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>

组件组合

组件Props传参

Vue 3

<script setup>
import UserProfile from "./UserProfile.vue";
</script>

<template>
  <UserProfile
    name="张三"
    :age="20"
    :favourite-colors="['green', 'blue', 'red']"
    is-available
  />
</template>

Svelte 4

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

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

向父组件emit事件

Vue 3

<script setup>
import { ref } from "vue";
import AnswerButton from "./AnswerButton.vue";

let isHappy = ref(true);

function onAnswerNo() {
  isHappy.value = false;
}

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

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

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>

slot插槽

Vue 3

<script setup>
import FunnyButton from "./FunnyButton.vue";
</script>

<template>
  <FunnyButton> 点我! </FunnyButton>
</template>

Svelte 4

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

<FunnyButton>点我!</FunnyButton>

slot插槽内容

Vue 3

<script setup>
import FunnyButton from "./FunnyButton.vue";
</script>

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

Svelte 4

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

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

上下文

Vue 3

<script setup>
import { ref, provide } from "vue";
import UserProfile from "./UserProfile.vue";

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

function updateUsername(username) {
  user.value.username = username;
}

provide("user", { user, updateUsername });
</script>

<template>
  <h1>欢迎回来, {{ user.username }}</h1>
  <UserProfile />
</template>

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 />

表单输入

输入框

Vue 3

<script setup>
import { ref } from "vue";
const text = ref("你好世界");
</script>

<template>
  <p>{{ text }}</p>
  <input v-model="text" />
</template>

Svelte 4

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

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

复选框

Vue 3

<script setup>
import { ref } from "vue";

const isAvailable = ref(true);
</script>

<template>
  <input id="is-available" v-model="isAvailable" type="checkbox" />
  <label for="is-available">这是一个checkbox</label>
</template>

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>

单选框

Vue 3

<script setup>
import { ref } from "vue";

const picked = ref("red");
</script>

<template>
  <div>你选择了: {{ picked }}</div>

  <input id="blue-pill" v-model="picked" type="radio" value="blue" />
  <label for="blue-pill">蓝色</label>

  <input id="red-pill" v-model="picked" type="radio" value="red" />
  <label for="red-pill">红色</label>
</template>

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>

选择器

Vue 3

<script setup>
import { ref } from "vue";

const selectedColorId = ref(2);

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

<template>
  <select v-model="selectedColorId">
    <option
      v-for="color in colors"
      :key="color.id"
      :value="color.id"
      :disabled="color.isDisabled"
    >
      {{ color.text }}
    </option>
  </select>
</template>

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>

Web应用特性

渲染应用

Vue 3

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

Svelte 4

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

fetch获取数据

Vue 3

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

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

<template>
  <p v-if="isLoading">正在获取用户信息……</p>
  <p v-else-if="error">获取用户信息出错</p>
  <ul v-else-if="users">
    <li v-for="user in users" :key="user.login.uuid">
      <img :src="user.picture.thumbnail" alt="user" />
      <p>
        {{ user.name.first }}
        {{ user.name.last }}
      </p>
    </li>
  </ul>
</template>

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}

响应式 #

声明状态 #

Vue 3

Svelte 4

更新状态 #

Vue 3

Svelte 4

计算属性 #

Vue 3

Svelte 4

模板语法 #

最简模板 #

Vue 3

Svelte 4

样式 #

Vue 3

Svelte 4

DOM循环 #

Vue 3

Svelte 4

点击事件 #

Vue 3

Svelte 4

DOM引用 #

Vue 3

Svelte 4

条件渲染 #

Vue 3

Svelte 4

生命周期 #

组件加载时 #

Vue 3

Svelte 4

组件卸载时 #

Vue 3

Svelte 4

组件组合 #

组件Props传参 #

Vue 3

Svelte 4

向父组件emit事件 #

Vue 3

Svelte 4

slot插槽 #

Vue 3

Svelte 4

slot插槽内容 #

Vue 3

Svelte 4

上下文 #

Vue 3

Svelte 4

表单输入 #

输入框 #

Vue 3

Svelte 4

复选框 #

Vue 3

Svelte 4

单选框 #

Vue 3

Svelte 4

选择器 #

Vue 3

Svelte 4

Web应用特性 #

渲染应用 #

Vue 3

Svelte 4

fetch获取数据 #

Vue 3

Svelte 4

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