if(isMouseDown){
let preArea = ele.getElementsByClassName('v-selected-area')
if(preArea.length){
ele.removeChild(preArea[0])
}
reactArea.endX = e.layerX
reactArea.endY = e.layerY
let leftValue = 0
let topValue = 0
let widthValue = Math.abs(reactArea.startX - reactArea.endX)
let heightValue = Math.abs(reactArea.startY - reactArea.endY)
if(reactArea.startX >= reactArea.endX){
leftValue = reactArea.endX
}else{
leftValue = reactArea.startX
}
if(reactArea.startY > reactArea.endY ){
topValue = reactArea.endY
}else{
topValue = reactArea.startY
}
//判断同时有宽高才开始画虚线框
if(reactArea.startX != reactArea.endX && reactArea.startY !=reactArea.endY){
areaSelect = document.createElement('div')
areaSelect.classList.add("v-selected-area")
areaSelect.style.position = "absolute";
areaSelect.style.left = leftValue + 'px'
areaSelect.style.top = topValue + 'px'
areaSelect.style.width = widthValue + 'px'
areaSelect.style.height = heightValue + 'px'
areaSelect.style.border = "1px dashed grey"
ele.append(areaSelect)
}
let children = ele.getElementsByTagName('li')
for(let i =0 ; i < children.length ; i ++ ){
let childrenHeight = children[i].getBoundingClientRect().height
let childrenWidth = children[i].getBoundingClientRect().width
//每个li元素的位置
let offsetLeft = children[i].offsetLeft
let offsetTop = children[i].offsetTop
//每个li元素的宽高
let endPositionH = childrenHeight + offsetTop
let endPositionW = childrenWidth + offsetLeft
//五个条件满足一个就可以判断被选择
//一是右下角在选择区域内
let require1 = endPositionH > topValue && endPositionW > leftValue && endPositionH < topValue + heightValue && endPositionW < leftValue + widthValue
//二是左上角在选择区域内
let require2 = offsetTop > topValue && offsetLeft > leftValue && offsetTop < topValue + heightValue && offsetLeft < leftValue + widthValue
//三是右上角在选择区域内
let require3 = offsetTop > topValue && offsetLeft + childrenWidth > leftValue && offsetTop < topValue + heightValue && offsetLeft + childrenWidth< leftValue + widthValue
//四是左下角在选择区域内
let require4 = offsetTop + childrenHeight > topValue && offsetLeft > leftValue && offsetTop + childrenHeight < topValue + heightValue && offsetLeft < leftValue + widthValue
//五选择区域在元素体内
let require5 = offsetTop < topValue && offsetLeft < leftValue && offsetTop + childrenHeight > topValue + heightValue && offsetLeft + childrenWidth > leftValue + widthValue
