如何确定隐藏/溢出文本位于元素的顶部还是底部

你可以合并 scrollLeft scrollTop 用肖格的回答。

// Author: Shog9
// Determines if the passed element is overflowing its bounds,
// either vertically or horizontally.
// Will temporarily modify the "overflow" style to detect this
// if necessary.
// Modified to check if the user has scrolled right or down.
function checkOverflow(el)
{
   var curOverflow = el.style.overflow;
   if ( !curOverflow || curOverflow === "visible" )
      el.style.overflow = "hidden";

   var isOverflowing = el.clientWidth < el.scrollWidth 
      || el.clientHeight < el.scrollHeight;

   // check scroll location
   var isScrolledRight = el.scrollLeft > 0;
   var isScrolledDown = el.scrollTop > 0;

   el.style.overflow = curOverflow;

   return isOverflowing;
}

透过树林我看不见森林。乔尔的代码片段 var isScrolledDown = el.scrollTop > 0; 让我意识到怎么做。我使用了两个函数:

function HasTopOverflow(el) {
   return el.scrollTop;
}

function HasBottomOverflow(el) {
   var scrollTop = el.scrollTop,
       clientHeight = el.clientHeight,
       scrollHeight = Math.max(el.scrollHeight, clientHeight);

   return (scrollTop + clientHeight) < scrollHeight;
}

尚未测试它是否能在IE6+上工作,但FF可以工作。