vue自定义指令directive的使用场景

 // 注册
    Vue.directive('my-directive',{
        bind:  function () {},         
        inserted: function () {},
        update: function () {},
        componentUpdated: function () {},
        unbind: function() {}
    })

import Vue from 'vue'
import { Message } from 'element-ui';


// 自定义指令示例1：弹窗拖拽
Vue.directive('dialogDrag',{
    bind(el,binding,vnode,oldVnode){
        const dialogHeader = el.querySelector('.el-dialog__header');
        const dialogDom = el.querySelector('.el-dialog');
        dialogHeader.style.cursor = 'move'

        
        const sty = dialogDom.currentStyle || window.getComputedStyle(dialogDom, null)

        dialogHeader.onmousedown = (e) => {
            //按下鼠标，获取点击的位置 距离 弹窗的左边和上边的距离
            //点击的点距离左边窗口的距离 - 弹窗距离左边窗口的距离
            const distX = e.clientX - dialogHeader.offsetLeft;
            const distY = e.clientY - dialogHeader.offsetTop;

            //弹窗的left属性值和top属性值
            let styL, styT

            //注意在ie中，第一次获取到的值为组件自带50%，移动之后赋值为Px
            if(sty.left.includes('%')){
                styL = +document.body.clientWidth * (+sty.left.replace(/%/g,'') / 100)
                styT = +document,body.clientHeight * (+sty.top.replace(/%/g,'') / 100)
            }else{
                styL = +sty.left.replace(/px/g,'');
                styT = +sty.top.replace(/px/g,'');
            }

            document.onmousemove = function(e) {
                //通过事件委托，计算移动距离
                const l = e.clientX - distX
                const t = e.clientY - distY

                //移动当前的元素
                dialogDom.style.left = `${l + styL}px`
                dialogDom.style.top = `${t + styT}px`
            }

            document.onmouseup = function(e){
                document.onmousemove = null
                document.onmouseup = null
            }
        }
    }
})

//自定义指令示例2：v-dialogDragWidth 可拖动弹窗宽度（右侧边）
Vue.directive('dragWidth',{
  bind(el) {
      const dragDom = el.querySelector('.el-dialog');
      const lineEl = document.createElement('div');
      lineEl.style = 'width: 5px; background: inherit; height: 80%; position: absolute; right: 0; top: 0; bottom: 0; margin: auto; z-index: 1; cursor: w-resize;';
      lineEl.addEventListener('mousedown',
          function (e) {
              // 鼠标按下，计算当前元素距离可视区的距离
              const disX = e.clientX - el.offsetLeft;
              // 当前宽度
              const curWidth = dragDom.offsetWidth;
              document.onmousemove = function (e) {
                  e.preventDefault(); // 移动时禁用默认事件
                  // 通过事件委托，计算移动的距离
                  const l = e.clientX - disX;
                  if(l > 0){
                      dragDom.style.width = `${curWidth + l}px`;
                  }
              };
              document.onmouseup = function (e) {
                  document.onmousemove = null;
                  document.onmouseup = null;
              };
          }, false);
      dragDom.appendChild(lineEl);
  }
})

// 自定义指令示例3：v-dialogDragWidth 可拖动弹窗高度（右下角）
Vue.directive('dragHeight',{
  bind(el) {
      const dragDom = el.querySelector('.el-dialog');
      const lineEl = document.createElement('div');
      lineEl.style = 'width: 6px; background: inherit; height: 10px; position: absolute; right: 0; bottom: 0; margin: auto; z-index: 1; cursor: nwse-resize;';
      lineEl.addEventListener('mousedown',
          function(e) {
              // 鼠标按下，计算当前元素距离可视区的距离
              const disX = e.clientX - el.offsetLeft;
              const disY = e.clientY - el.offsetTop;
              // 当前宽度 高度
              const curWidth = dragDom.offsetWidth;
              const curHeight = dragDom.offsetHeight;
              document.onmousemove = function(e) {
                  e.preventDefault(); // 移动时禁用默认事件
                  // 通过事件委托，计算移动的距离
                  const xl = e.clientX - disX;
                  const yl = e.clientY - disY
                  dragDom.style.width = `${curWidth + xl}px`;
                  dragDom.style.height = `${curHeight + yl}px`;
              };
              document.onmouseup = function(e) {
                  document.onmousemove = null;
                  document.onmouseup = null;
              };
          }, false);
      dragDom.appendChild(lineEl);
  }
})

// 自定义指令示例4：图片加载前填充背景色
Vue.directive('imgUrl',function(el,binding){
    var color=Math.floor(Math.random()*1000000);//设置随机颜色
    el.style.backgroundColor='#'+color;
   
    var img=new Image();
    img.src=binding.value;// -->binding.value指的是指令后的参数
    img.onload=function(){
      el.style.backgroundColor='';
      el.src=binding.value;      
    }
  })

// 自定义指令示例5：输入框聚焦
Vue.directive("focus", {
    // 当被绑定的元素插入到 DOM 中时……
    inserted (el) {
        // 聚焦元素
        el.querySelector('input').focus()
    },
  });

// 自定义指令示例6：设置防抖自定义指令
Vue.directive('throttle', {
    bind: (el, binding) => {
      let setTime = binding.value; // 可设置防抖时间
      if (!setTime) { // 用户若不设置防抖时间，则默认2s
        setTime = 1000;
      }
      let cbFun;
      el.addEventListener('click', event => {
        if (!cbFun) { // 第一次执行
          cbFun = setTimeout(() => {
            cbFun = null;
          }, setTime);
        } else {
            
          event && event.stopImmediatePropagation();
        }
      }, true);
    },
  });

// 自定义指令示例7：点击按钮操作频繁给出提示
  Vue.directive('preventReClick', {
    inserted: function (el, binding) {
      el.addEventListener('click', () => {
        if (!el.disabled) {
          el.disabled = true
          Message.warning('操作频繁')
          setTimeout(() => {
            el.disabled = false
            //可设置时间
          }, binding.value || 3000)
        }
      })
    }
})
  

import '@/assets/js/drag.js'

<template>
  <div>
    <el-button type="text" @click="dialogVisible = true">点击打开 Dialog</el-button>
    <div style="display:flex">
      <img v-imgUrl="url"></img> 
      <img v-imgUrl="url"></img> 
      <img v-imgUrl="url"></img> 
      <img v-imgUrl="url"></img> 
      <img v-imgUrl="url"></img> 
      <img v-imgUrl="url"></img> 
      <img v-imgUrl="url"></img> 
      <img v-imgUrl="url"></img> 
    </div>
    <div>
      <el-input  placeholder="请选择日期" suffix-icon="el-icon-date"  v-model="input1"></el-input>
      <el-input v-focus placeholder="请输入内容" prefix-icon="el-icon-search" v-model="input2"></el-input>
    </div>

    <div>
      <el-button type="danger" v-throttle @click="throttleBtn">危险按钮</el-button>
      <el-button @click="submitFORM()">创建</el-button>
    </div>

    <el-dialog title="提示" v-dialogDrag v-dragWidth v-dragHeight :visible.sync="dialogVisible" width="30%" :before-close="handleClose">
      <span>这是一段信息</span>
      <span slot="footer" class="dialog-footer">
        <el-button @click="dialogVisible = false">取 消</el-button>
        <el-button type="primary" @click="dialogVisible = false">确 定</el-button>
      </span>
    </el-dialog>
  </div>
</template>

<script>

export default {

  data() {
    return {
      dialogVisible: false,
      url:'//www.baidu.com/img/flexible/loGo/pc/result.png',
      input1: '',
      input2: '',
    }
  },
  methods: {
    handleClose(done) {
      console.log('弹窗打开')  
    },
    throttleBtn(){
      console.log('我的用来测试防抖的按钮')
    },
    submitForm(){
      this.$message.error('Message 消息提示每次只能1个');
    }
  },
}
</script>
<style>
img{
  width: 100px;
  height: 100px;
}
</style>