vue2自定义指令，弹窗拖拽，设置拖拽界限

import Vue from 'vue'
// v-dialogDrag: 弹窗拖拽自定义指令，已在main.js引入,使用即可，每个 el-dialog 加指令
Vue.directive('dialogDrag', {
    bind(el, binding, vnode, oldVnode) {
        /**
         * 关闭弹窗可移动
         * @type {CustomEvent}
         */
        // return;

        /**
         * 打开弹窗可移动
          * @type {CustomEvent}
         */    
        let resizeEvent = new CustomEvent('drag-resize',{detail:'尺寸变化',bubbles:false});
        //初始化不最大化
        el.fullscreen = false;
        //弹框可拉伸最小宽高
        let minWidth = 400;
        let minHeight = 300;
        //当前宽高
        let nowWidth = minWidth;
        let nowHight = minHeight;
        //当前顶部高度
        let nowMarginTop = 0;
        //获取弹框头部（这部分可双击全屏）
        const dialogHeaderEl = el.querySelector('.el-dialog__header');
        let hasSetBodyHight = false;
        //弹窗
        const dragDom = el.querySelector('.el-dialog');
        dragDom.className += ' el-drag-dialog';
        //清除选择头部文字效果
        dialogHeaderEl.onselectstart = new Function("return false");
        //头部加上可拖动cursor
        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);
        //头部插入最大化最小化元素
        let maxMin = document.createElement("button");
        maxMin.className += ' el-dialog__headerbtn el-dialog__minmax';
        maxMin.style.right = '40px';
        maxMin.style.color = '#909399';
        maxMin.title = el.fullscreen ? '还原' : '最大化';
        maxMin.innerHTML = '<i class=' + (el.fullscreen ? '"el-icon-crop"' : '"el-icon-full-screen"') + ' onMouseOver="this.style.color=\'#409EFF\'" onMouseOut="this.style.color=\'inherit\'"></i>';
        dialogHeaderEl.insertBefore(maxMin, dialogHeaderEl.childNodes[1]);
        let moveDown = (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;

            // 获取到的值带px 正则匹配替换
            let styL, styT;

            const screenWidth = document.documentElement.clientWidth || document.body.clientWidth // 页面可视区宽度，兼容写法
            const screenHeight = document.documentElement.clientHeight || document.body.clientHeight // 页面可视区高度，兼容写法
            
            const dragDomWidth = dragDom.offsetWidth // 对话框宽度
            const dragDomheight = dragDom.offsetHeight // 对话框高度
            // 下面四行的是 x轴和y轴最小和最大的移动范围  可基于上面两行设置
            const minDragDomLeft = (dragDom.offsetLeft+dragDomWidth/2) // 对话框边界最小left值
            const maxDragDomLeft = (screenWidth - dragDom.offsetLeft - dragDomWidth+dragDomWidth/2) // 对话框边界最大left值
      
            const minDragDomTop = dragDom.offsetTop // 对话框边界最小Top值
            const maxDragDomTop = (screenHeight - dragDom.offsetTop - dragDomheight+dragDomheight/2) // 对话框边界最大Top值

            // 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，计算移动的距离
                let l = e.clientX - disX;
                let 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
                }
                console.log(`${l + styL}px`,`${t + styT}px`);
                // 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;
            };
        }
        dialogHeaderEl.onmousedown = moveDown;
        let bodyHeight = 'auto';
        // 最大/最小化
        function setMaxMin() {
            if (el.fullscreen) {
                let i = maxMin.querySelector('.el-icon-crop');
                i.classList.remove('el-icon-crop');
                i.classList.add('el-icon-full-screen');
                maxMin.innerHTML = '<i class="el-icon-full-screen"></i>';
                maxMin.title = '最大化';
                dragDom.style.height = "auto";
                dragDom.style.width = nowWidth + 'px';
                dragDom.style.marginTop = nowMarginTop;
                el.fullscreen = false;
                dialogHeaderEl.style.cursor = 'move';
                dialogHeaderEl.onmousedown = moveDown;
                dragDom.querySelector('.el-dialog__body').style.height = bodyHeight;
                hasSetBodyHight = false;
            } else {
                let i = maxMin.querySelector('.el-icon-full-screen');
                i.classList.remove('el-icon-full-screen');
                i.classList.add('el-icon-crop');
                maxMin.title = '还原';
                bodyHeight = dragDom.querySelector('.el-dialog__body').offsetHeight + 'px';
                nowHight = dragDom.clientHeight;
                nowWidth = dragDom.clientWidth;
                nowMarginTop = dragDom.style.marginTop;
                dragDom.style.left = 0;
                dragDom.style.top = 0;
                dragDom.style.height = "100VH";
                dragDom.style.width = "100VW";
                dragDom.style.marginTop = 0;
                el.fullscreen = true;
                dialogHeaderEl.style.cursor = 'initial';
                dialogHeaderEl.onmousedown = null;
                if (!hasSetBodyHight) {
                    let footerHeight = dragDom.querySelector('.el-dialog__footer') && dragDom.querySelector('.el-dialog__footer').offsetHeight;
                    dragDom.querySelector('.el-dialog__body').style.height = 'calc(100% - ' + (dialogHeaderEl.offsetHeight + footerHeight) + 'px)';
                    hasSetBodyHight = true;
                }
            }
            el.dispatchEvent(resizeEvent);
        }

        //点击放大缩小效果
        maxMin.onclick = setMaxMin;
        //双击头部效果
        dialogHeaderEl.ondblclick = setMaxMin;
        //获取弹框底部（这部分可双击全屏）
        const dialogFooter = el.querySelector('.el-dialog__footer');
        if (dialogFooter) {
            dialogFooter.ondblclick = setMaxMin;
        }
        //拉伸
        let resizeEl = document.createElement("div");
        dragDom.appendChild(resizeEl);
        //在弹窗右下角加上一个10-10px的控制块
        resizeEl.style.cursor = 'se-resize';
        resizeEl.style.position = 'absolute';
        resizeEl.style.height = '10px';
        resizeEl.style.width = '10px';
        resizeEl.style.right = '0px';
        resizeEl.style.bottom = '0px';
        //鼠标拉伸弹窗
        resizeEl.onmousedown = (e) => {
            // 记录初始x位置
            const clientX = e.clientX;
            // 鼠标按下，计算当前元素距离可视区的距离
            const disX = e.clientX - resizeEl.offsetLeft;
            const disY = e.clientY - resizeEl.offsetTop;
            document.onmousemove = function (e) {
                // 通过事件委托，计算移动的距离 （开始拖拽至结束拖拽的距离）

                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 x = e.clientX - disX + (e.clientX - clientX);//这里 由于elementUI的dialog控制居中的，所以水平拉伸效果是双倍
                const y = e.clientY - disY;

                //比较是否小于最小宽高
                dragDom.style.width = x > minWidth ? `${x}px` : minWidth + 'px';
                dragDom.style.height = y > minHeight ? `${y}px` : minHeight + 'px';
                if (!hasSetBodyHight) {
                    let footerHeight = dragDom.querySelector('.el-dialog__footer') && dragDom.querySelector('.el-dialog__footer').offsetHeight;
                    dragDom.querySelector('.el-dialog__body').style.height = 'calc(100% - ' + (dialogHeaderEl.offsetHeight + footerHeight) + 'px)';
                    hasSetBodyHight = true;
                }
            };
            //拉伸结束
            document.onmouseup = function (e) {
                document.onmousemove = null;
                document.onmouseup = null;
                el.dispatchEvent(resizeEvent);
            };
        }
    },
})

最后在main.js进行全局引入
页面标签中使用v-dialogDrag 指令即可