再ulits新建一个directive.js文件，再main.js中引入

以下为directive.js的代码（全）

import Vue from 'vue'

// v-dialogDrag: 弹窗拖拽
Vue.directive('dialogDrag', {
  bind (el, binding, vnode, oldVnode) {
    const dialogHeaderEl = el.querySelector('.el-dialog__header')
    const dragDom = el.querySelector('.el-dialog')
    dialogHeaderEl.style.cursor = 'move'

    // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);
    const sty = dragDom.currentStyle || window.getComputedStyle(dragDom, null)

    dialogHeaderEl.onmousedown = (e) => {
      // 鼠标按下，计算当前元素距离可视区的距离
      const disX = e.clientX - dialogHeaderEl.offsetLeft
      const disY = e.clientY - dialogHeaderEl.offsetTop
      const screenWidth = document.body.clientWidth; // body当前宽度
      const screenHeight = document.documentElement.clientHeight; // 可见区域高度(应为body高度，可某些环境下无法获取)
      const dragDomWidth = dragDom.offsetWidth; // 对话框宽度
      const dragDomheight = dragDom.offsetHeight; // 对话框高度
      const minDragDomLeft = dragDom.offsetLeft;
      const maxDragDomLeft = screenWidth - dragDom.offsetLeft - dragDomWidth;
      const minDragDomTop = dragDom.offsetTop;
      const maxDragDomTop = screenHeight - dragDom.offsetTop - dragDomheight;

      // 获取到的值带px 正则匹配替换
      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) {
        // 获取body的页面可视宽高
        // var clientHeight = document.documentElement.clientHeight || document.body.clientHeight
        // var clientWidth = document.documentElement.clientWidth || document.body.clientWidth

        // 通过事件委托，计算移动的距离
        var l = e.clientX - disX
        var t = e.clientY - disY

        // 边界处理
        if (-l > minDragDomLeft) {
          l = -minDragDomLeft;
        } else if (l > maxDragDomLeft) {
          l = maxDragDomLeft;
        }
        if (-t > minDragDomTop) {
          t = -minDragDomTop;
        } else if (t > maxDragDomTop) {
          t = maxDragDomTop;
        }
        // 移动当前元素
        dragDom.style.left = `${l + styL}px`
        dragDom.style.top = `${t + styT}px`

        // 将此时的位置传出去
        // binding.value({x:e.pageX,y:e.pageY})
      }

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

// v-dialogDragWidth: 弹窗宽度拖大 拖小
/** Vue.directive('dialogDragWidth', {
  bind (el, binding, vnode, oldVnode) {
    const dragDom = binding.value.$el.querySelector('.el-dialog')

    el.onmousedown = (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

      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
        dragDom.style.width = `${l}px`
      }

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

dialog弹框中使用，添加 v-dialogDrag

  <el-dialog
      @close="resObjdia(index)"
      :close-on-press-escape="false"
      :close-on-click-modal="false"
      v-dialogDrag
      class="resObj"
      title="返回参数详情"
      :visible.sync="resObjdialog"
      width="40%">
      <pre class="pre" v-for="(i,index) in resObject" :key="index"  v-show="indexBeforetableData == index">{{i}}</pre>
      <span slot="footer" class="dialog-footer">
          <el-button type="primary" @click="resObjdialog = false">确 定</el-button>
      </span>
  </el-dialog>

再点击这个弹框，就有拖拽效果啦。做了边界处理，不会超出浏览器可视范围。