除了 Vue 内置的一系列指令 (比如 v-model 或 v-show) 之外，Vue 还允许你注册自定义的指令 (Custom Directives)。
1. 生命周期钩子函数
一个自定义指令由一个包含类似组件生命周期钩子的对象来定义。钩子函数会接收到指令所绑定元素作为其参数。
在 <script setup> 中，任何以 v 开头的驼峰式命名的变量都可以被用作一个自定义指令。
<!-- App.vue --> <template> <div> <button>切换</button> <!-- 钩子函数里面都可以接受这些值 myParam: 自定义参数； myModifier: 自定义修饰符 --> <A v-move:myParam.myModifier="{ background: 'pink' }"></A> </div> </template> <script setup lang="ts"> import { reactive, ref, Directive } from 'vue'; import A from './components/A.vue'; import B from './components/B.vue'; let flag = ref<boolean>(true) const vMove: Directive = { created() { console.log('created') }, beforeMount() { console.log('beforeMount') }, mounted(...args: Array<any>) { console.log('mounted') console.log(args); }, beforeUpdate() { console.log('beforeUpdate') }, updated() { console.log('updated') }, beforeUnmount() { console.log('beforeUnmount') }, unmounted() { console.log('unmounted') } } </script> <style scoped lang="less"></style>
- 0：该 div 元素。
- 1：传入的参数等。比如 arg 参数，modifiers 自定义修饰符，dir 目录，传入的 value 值，instance 组件实例。
- 2：当前组件的虚拟 DOM
- 3：上一个虚拟 DOM
<!-- App.vue --> <template> <div> <button>切换</button> <!-- 钩子函数里面都可以接受这些值 myParam: 自定义参数； myModifier: 自定义修饰符 --> <A v-move:myParam.myModifier="{ background: 'pink' }"></A> </div> </template> <script setup lang="ts"> import { reactive, ref, Directive, DirectiveBinding } from 'vue'; import A from './components/A.vue'; import B from './components/B.vue'; let flag = ref<boolean>(true) type Dir = { background: string; } const vMove: Directive = { created() { console.log('created') }, beforeMount() { console.log('beforeMount') }, mounted(el: HTMLElement, dir: DirectiveBinding<Dir>) { console.log('mounted') console.log(el); console.log(dir); el.style.background = dir.value.background; }, // 传入的数据发生变化（比如此时的background）时触发 beforeUpdate 和 updated beforeUpdate() { console.log('beforeUpdate') }, updated() { console.log('updated') }, beforeUnmount() { console.log('beforeUnmount') }, unmounted() { console.log('unmounted') } } </script> <style scoped lang="less"></style>
2. 指令简写
<!-- App.vue --> <template> <div class="btns"> <button v-has-show="123">创建</button> <button>编辑</button> <button>删除</button> </div> </template> <script setup lang="ts"> import { reactive, ref, DirectiveBinding } from 'vue'; import type { Directive } from 'vue' const vHasShow: Directive = (el, binding) => { console.log(el, binding) ; } </script> <style scoped lang="less"> .btns { button { margin: 10px; } } </style>
应用场景1：按钮鉴权
根据能否从 localStorage（或者后台返回） 中获取数据，来判断是否显示某个按钮。
<!-- App.vue --> <template> <div class="btns"> <button v-has-show="'shop:create'">创建</button> <button v-has-show="'shop:edit'">编辑</button> <button v-has-show="'shop:delete'">删除</button> </div> </template> <script setup lang="ts"> import { reactive, ref, DirectiveBinding } from 'vue'; import type { Directive } from 'vue' localStorage.setItem('userId', 'xiuxiu') // mock 后台返回的数据 const permissions = [ 'xiuxiu:shop:create', // 'xiuxiu:shop:edit', // 后台没有相应数据，则不显示该对应的按钮 'xiuxiu:shop:delete' ] const userId = localStorage.getItem('userId') as string const vHasShow: Directive = (el, binding) => { if(!permissions.includes(userId + ':' + binding.value)) { el.style.display = 'none' } } </script> <style scoped lang="less"> .btns { button { margin: 10px; } } </style>
应用场景2：鼠标拖拽
拖拽粉色框移动大盒子。
<!-- App.vue --> <template> <div v-move class="box"> <div class="header"></div> <div>内容</div> </div> </template> <script setup lang="ts"> import { Directive, DirectiveBinding } from 'vue'; const vMove:Directive<any,void> = (el:HTMLElement, binding:DirectiveBinding)=> { let moveElement:HTMLElement = el.firstElementChild as HTMLElement; console.log(moveElement); const mouseDown = (e:MouseEvent) => { // 记录原始位置 // clientX 鼠标点击位置的X轴坐标 // clientY 鼠标点击位置的Y轴坐标 // offsetLeft 鼠标点击的子元素距离其父元素的左边的距离 // offsetTop 鼠标点击的子元素距离其父元素的顶部的距离 let X = e.clientX - el.offsetLeft; let Y = e.clientY - el.offsetTop; const move = (e:MouseEvent) => { console.log(e); el.style.left = e.clientX - X + 'px'; el.style.top = e.clientY - Y + 'px'; } document.addEventListener('mousemove', move); document.addEventListener('mouseup', () => { document.removeEventListener('mousemove', move); }) } moveElement.addEventListener('mousedown', mouseDown); } </script> <style scoped lang="less"> .box { position: fixed; height: 200px; width: 200px; top: 50%; left: 50%; transform: translate(-50%, -50%); border: 1px solid #000; .header { height: 50px; width: 100%; background: pink; border-bottom: #000 1px solid; } } </style>
应用场景3：懒加载
let imageList = import.meta.glob('./assets/images/*.*', { eager: true })
let imageList = import.meta.glob('./assets/images/*.*')
// 判断图片是否在可视区 const observer = new IntersectionObserver((e)=> { console.log(e[0]); }) // 监听元素 observer.observe(el)
<!-- App.vue --> <template> <div> <div> <img v-lazy="item" width="400" height="500" v-for="item in arr" alt=""> </div> </div> </template> <script setup lang="ts"> import { Directive, DirectiveBinding } from 'vue'; let imageList:Record<string,{default:string}> = import.meta.glob('./assets/images/*.*', { eager: true }) let arr = Object.values(imageList).map(item=>item.default) console.log(arr); let vLazy:Directive<HTMLImageElement,string> = async (el,binding)=> { const def = await import('./assets/pinia.svg') el.src = def.default // 判断图片是否在可视区 const observer = new IntersectionObserver((e)=> { console.log(e[0],binding.value); if(e[0].intersectionRatio > 0) { setTimeout(()=> { el.src = binding.value },2000) observer.unobserve(el) } }) // 监听元素 observer.observe(el) } </script> <style scoped lang="less"></style>
