Vue 3 vs Vue 2 - 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>

Vue 2

<script>
export default {
  data() {
    return {
      name: "张三",
    };
  },
};
</script>

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

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>

Vue 2

<script>
export default {
  data() {
    return {
      name: "张三",
    };
  },
  created() {
    this.name = "李四";
  },
};
</script>

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

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>

Vue 2

<script>
export default {
  data() {
    return {
      count: 10,
    };
  },
  computed: {
    doubleCount() {
      return this.count * 2;
    },
  },
};
</script>

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

模板语法

最简模板

Vue 3

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

Vue 2

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

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>

Vue 2

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

<style scoped>
.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>

Vue 2

<script>
export default {
  data() {
    return {
      colors: ["红", "绿", "蓝"],
    };
  },
};
</script>

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

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>

Vue 2

<script>
export default {
  data() {
    return {
      count: 0,
    };
  },
  methods: {
    incrementCount() {
      this.count++;
    },
  },
};
</script>

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

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>

Vue 2

<script>
export default {
  mounted() {
    this.$refs.inputElement.focus();
  },
};
</script>

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

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>

Vue 2

<script>
export default {
  data() {
    return {
      TRAFFIC_LIGHTS: ["红灯", "黄灯", "绿灯"],
      lightIndex: 0,
    };
  },
  computed: {
    light() {
      return this.TRAFFIC_LIGHTS[this.lightIndex];
    },
  },
  methods: {
    nextLight() {
      this.lightIndex = (this.lightIndex + 1) % this.TRAFFIC_LIGHTS.length;
    },
  },
};
</script>

<template>
  <div>
    <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>
  </div>
</template>

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>

Vue 2

<script>
export default {
  data() {
    return {
      pageTitle: "",
    };
  },
  mounted() {
    this.pageTitle = document.title;
  },
};
</script>

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

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>

Vue 2

<script>
export default {
  data() {
    return {
      time: new Date().toLocaleTimeString(),
      timer: null,
    };
  },
  mounted() {
    this.timer = setInterval(() => {
      this.time = new Date().toLocaleTimeString();
    }, 1000);
  },
  beforeDestroy() {
    clearInterval(this.timer);
  },
};
</script>

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

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>

Vue 2

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

export default {
  components: {
    UserProfile,
  },
};
</script>

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

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>

Vue 2

<script>
import AnswerButton from "./AnswerButton.vue";
export default {
  components: {
    AnswerButton,
  },
  data() {
    return {
      isHappy: true,
    };
  },
  methods: {
    onAnswerNo() {
      this.isHappy = false;
    },
    onAnswerYes() {
      this.isHappy = true;
    },
  },
};
</script>

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

slot插槽

Vue 3

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

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

Vue 2

<script>
import FunnyButton from "./FunnyButton.vue";
export default {
  components: {
    FunnyButton,
  },
};
</script>

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

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>

Vue 2

<script>
import FunnyButton from "./FunnyButton.vue";
export default {
  components: {
    FunnyButton,
  },
};
</script>

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

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>

Vue 2

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

export default {
  components: { UserProfile },
  provide() {
    return {
      user: Object.assign(this.user, {
        updateUsername: this.updateUsername,
      }),
    };
  },
  data() {
    return {
      user: {
        id: 1,
        username: "abcdefg",
        email: "[email protected]",
      },
    };
  },
  methods: {
    updateUsername(newUsername) {
      this.user.username = newUsername;
    },
  },
};
</script>

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

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>

Vue 2

<script>
export default {
  data() {
    return {
      text: "你好世界",
    };
  },
};
</script>

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

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>

Vue 2

<script>
export default {
  data() {
    return {
      isAvailable: true,
    };
  },
};
</script>

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

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>

Vue 2

<script>
export default {
  data() {
    return {
      picked: "red",
    };
  },
};
</script>

<template>
  <div>
    <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>
  </div>
</template>

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>

Vue 2

<script>
export default {
  data() {
    return {
      selectedColorId: 2,
      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>

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>

Vue 2

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

Vue 2

<script>
export default {
  data() {
    return {
      isLoading: false,
      error: undefined,
      users: undefined,
    };
  },
  mounted() {
    this.fetchData();
  },
  methods: {
    async fetchData() {
      this.isLoading = true;
      try {
        const response = await fetch("https://randomuser.me/api/?results=3");
        const { results: users } = await response.json();
        this.users = users;
        this.error = undefined;
      } catch (error) {
        this.error = error;
      } finally {
        this.users = undefined;
        this.isLoading = false;
      }
    },
  },
};
</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>

响应式 #

声明状态 #

Vue 3

Vue 2

更新状态 #

Vue 3

Vue 2

计算属性 #

Vue 3

Vue 2

模板语法 #

最简模板 #

Vue 3

Vue 2

样式 #

Vue 3

Vue 2

DOM循环 #

Vue 3

Vue 2

点击事件 #

Vue 3

Vue 2

DOM引用 #

Vue 3

Vue 2

条件渲染 #

Vue 3

Vue 2

生命周期 #

组件加载时 #

Vue 3

Vue 2

组件卸载时 #

Vue 3

Vue 2

组件组合 #

组件Props传参 #

Vue 3

Vue 2

向父组件emit事件 #

Vue 3

Vue 2

slot插槽 #

Vue 3

Vue 2

slot插槽内容 #

Vue 3

Vue 2

上下文 #

Vue 3

Vue 2

表单输入 #

输入框 #

Vue 3

Vue 2

复选框 #

Vue 3

Vue 2

单选框 #

Vue 3

Vue 2

选择器 #

Vue 3

Vue 2

Web应用特性 #

渲染应用 #

Vue 3

Vue 2

fetch获取数据 #

Vue 3

Vue 2

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