export const drag = {
 
    inserted(el) {
 
        let oDiv = el
        
        //  左边距最大值   
        let maxLeft = el.parentNode.clientWidth - el.clientWidth
 
        //  上边距最大值    
        let maxTop = el.parentNode.clientHeight - el.clientHeight
 
        oDiv.onmousedown = function (e) {
            //  鼠标按下，计算当前元素距离可视区的距离
            let disX = e.clientX - oDiv.offsetLeft
 
            let disY = e.clientY - oDiv.offsetTop
 
            document.onmousemove = function (e) {
 
                //  获取到鼠标拖拽后的横向位移(距离父级元素)        
                let l = e.clientX - disX
 
                //  获取到鼠标拖拽后的纵向位移(距离父级元素)
                let t = e.clientY - disY
 
                oDiv.style.left = l + 'px'
 
                oDiv.style.top = t + 'px'
 
                if (e.clientX - disX <= 0) {
                    oDiv.style.left = 0 + 'px'
                }
 
                if (e.clientY - disY <= 0) {
                    oDiv.style.top = 0 + 'px'
                }
 
                if (e.clientX - disX >= maxLeft) {
                    oDiv.style.left = maxLeft + 'px'
                }
 
                if (e.clientY - disY >= maxTop) {
                    oDiv.style.top = maxTop + 'px'
                }
 
            }
 
            //    松开事件后，移除事件
 
            document.onmouseup = function () {
                document.onmousemove = null
                document.onmouseup = null
            }
        }
    }
}