使el-dialog实现弹窗拖拽

1.创建directive文件夹，里面创建directive.js文件

import Vue from 'vue';

Vue.directive('dialogDrag', {
  bind(el, binding, vnode, oldVnode) {
    const dialogHeaderEl = el.querySelector('.el-dialog__header');
    // const dialogHeaderEl = el.querySelector('.el-dialog__footer');
    const dragDom = el.querySelector('.el-dialog');
    //dialogHeaderEl.style.cursor = 'move';
    dialogHeaderEl.style.cssText += ';cursor:move;'
    dragDom.style.cssText += ''

    // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);
    const sty = (function () {
      if (window.document.currentStyle) {
        return (dom, attr) => dom.currentStyle[attr];
      } else {
        return (dom, attr) => getComputedStyle(dom, false)[attr];
      }
    })()

    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 + dragDomWidth;
      const maxDragDomLeft = screenWidth - dragDom.offsetLeft;

      const minDragDomTop = dragDom.offsetTop;
      const maxDragDomTop = screenHeight - dragDom.offsetTop;


      // 获取到的值带px 正则匹配替换
      let styL = sty(dragDom, 'left');
      let styT = sty(dragDom, 'top');

      // 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 (styL.includes('%')) {
        styL = +document.body.clientWidth * (+styL.replace(/\%/g, '') / 100);
        styT = +document.body.clientHeight * (+styT.replace(/\%/g, '') / 100);
      } else {
        styL = +styL.replace(/\px/g, '');
        styT = +styT.replace(/\px/g, '');
      }
      ;

      document.onmousemove = function (e) {
        // 通过事件委托，计算移动的距离
        let left = e.clientX - disX;
        let top = e.clientY - disY;

        // 边界处理
        if (-(left) > minDragDomLeft) {
          left = -(minDragDomLeft);
        } else if (left > maxDragDomLeft) {
          left = maxDragDomLeft;
        }

        if (-(top) > minDragDomTop) {
          top = -(minDragDomTop);
        } else if (top > maxDragDomTop) {
          top = maxDragDomTop;
        }

        // 移动当前元素
        dragDom.style.cssText += `;left:${left + styL}px;top:${top + styT}px;`;
      };

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

2.在main.js中全局引入

 import './directive/directives'

3.在vue页面中使用   v-dialogDrag

<el-dialog
        v-dialogDrag
>  </el-dialog>