offsetHeight,clientHeight,innerHeight,outerHeight,scrollHeight区别
元素偏移区域offsetWidth(border+padding+width)offsetHeight(border+padding+height)offsetLeft(元素距离定位父级左内边线的水平距离)offsetTop(元素距离定位父级上内边线的垂直距离)offsetParent(获取元素定位父级,父级加除了position:inherit|initial|static之外的定位属性则会得到