Vue3中自定义hook

hook，本质是一个函数。自定义hook，就是将setup中使用过的组合式函数进行封装，实现代码复用。

看个具体的例子吧。

• main.js

import { createApp } from 'vue'
import App from './App.vue'

createApp(App).mount('#app')

• App.vue

<template>
  <button @click="isShowDemo = !isShowDemo">切换（隐藏/显示）button>
  <Demo v-if="isShowDemo"/>
template>

<script>
import Demo from './components/Demo.vue'
import {ref} from "vue";
export default {
  name: 'App',
  components: {
    Demo
  },
  setup(){
    let isShowDemo = ref(true);
    
    return {isShowDemo};
  }
}
script>

• Demo.vue

<template>
  <h2>sum的当前值为：{{sum}}h2>
  <button @click="sum++">点我+1button>
  <hr>
  <h2>鼠标点击时的坐标，x:{{point.x}}，y:{{point.y}}h2>
template>

<script>
import {onBeforeUnmount, onMounted, ref,reactive} from "vue";

export default {
  name: 'Demo',
  setup(){
    let sum = ref(0);
    let point = reactive({
      x:0,
      y:0
    })

    function savePoint(event){
      point.x = event.pageX;
      point.y = event.pageY;
      console.log(event.pageX,event.pageY);
    }

    onMounted(() => {
      window.addEventListener("click",savePoint);
    })

    onBeforeUnmount(() => {
      window.removeEventListener("click",savePoint);
    })

    return {
      sum,
      point
    }
  }
}
script>

• 启动应用，测试效果
  
  Demo组件挂载后，鼠标点击页面上任意点，将显示该点的坐标。
  Demo组件被卸载后，将不再监听click事件。

接下来，我们将自定义hook：将point、savePoint、onMounted和onBeforeUnmount，即把数据、方法、和生命周期钩子封装在一个js文件。
在src目录下新建子目录hooks，并在hooks目录下新建文件：usePoint.js，如下所示。

import { reactive,onMounted,onBeforeUnmount } from "vue";

export default function(){
    let point = reactive({
        x:0,
        y:0
    });

    function savePoint(event){
        point.x = event.pageX;
        point.y = event.pageY;
        console.log(event.pageX,event.pageY);
    }

    onMounted(() => {
        window.addEventListener("click",savePoint);
    })

    onBeforeUnmount(() => {
        window.removeEventListener("click",savePoint);
    });

    return point;
}

然后修改Demo.vue，如下所示。

<template>
  <h2>sum的当前值为：{{sum}}h2>
  <button @click="sum++">点我+1button>
  <hr>
  <h2>鼠标点击时的坐标，x:{{point.x}}，y:{{point.y}}h2>
template>

<script>
import {ref} from "vue";
import usePoint from "../hooks/usePoint";

export default {
  name: 'Demo',
  setup(){
    let sum = ref(0);
    let point = usePoint();
    
    return {
      sum,
      point
    }
  }
}
script>