实现element-ui对话框可拖拽功能

directives.js:

import Vue from 'vue';
 
// 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;
        };
    }  
}

})

在main.js中引入:

import './directives.js';

在el-dialog标签中加入v-dialogDrag属性

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

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