最近在项目中用到了一个类似于微博的用户资料选项卡的功能，其实就是计算8个位置的坐标点
var screenW = $(window).width(),
screenH = $(window).height(),
domL = dom.offset().left,
domT = dom.offset().top,
domW = dom.outerWidth(),
domH = dom.outerHeight(),
usercardW = $("#usercard").outerWidth(),
usercardH = $("#usercard").outerHeight(),
scrollL = document.documentElement.scrollLeft || document.body.scrollLeft || 0,
scrollT = document.documentElement.scrollTop|| document.body.scrollTop || 0;
if(domL + scrollL < (screenW - 1000)/2 + 200){
if(screenH /2 < domT - scrollT){
return {top: domT + domH - usercardH + 'px', left : domL + domW + 'px'}
}else{
return {top: domT + 'px', left : domL + domW + 'px'}
}
}else if(domL + scrollL > screenW/2 + 200){
if(screenH /2 < domT - scrollT){
return {top: domT + domH - usercardH + 'px', left : domL - usercardW + 'px' }
}else{
return {top: domT + 'px', left : domL - usercardW + 'px'}
}
}else{
if(screenH /2 < domT - scrollT){
if(domL + scrollL < screenW/2){
return {top: domT - usercardH + 'px', left : domL + 'px'}
}else{
return {top: domT - usercardH + 'px', left : domL + domW - usercardW + 'px'}
}
}else{
if(domL + scrollL < screenW/2){
return {top: domT + domH + 'px', left : domL + 'px'}
}else{
return {top: domT + domH + 'px', left : domL + domW - usercardW + 'px'
}
}
}