getBoundingClientRect

{
  top: ‘元素顶部相对于视口顶部的距离‘,
  bottom: ‘元素底部相对于视口底部的距离‘,
  left: ‘元素左边相对于视口左边的距离‘,
  right: ‘元素右边相对于视口左边的距离‘,
  height: ‘元素高度‘,
  width: ‘元素宽度‘
}

// IE兼容性写法
function getClientReat(client) {
    const { top, bottom, left, right, height, width } = client.getBoundingClientRect()
    return {
        top,
        bottom,
        left,
        right,
        height: height || right - left,
        width:    width || bottom - top

    }
}