vue实现element-ui对话框可拖拽功能

// v-dialogDrag: 弹窗拖拽属性
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';
dialogHeaderEl.style.cssText += ';cursor:move;'
dragDom.style.cssText += ';top:0px;'

// 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;
    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 = 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;
  };
} 

}
})