开发过程中遇到这么一个问题有一个<select></select>的选择框，里面有个option的值很长大约128个字节，那么如果我不指定select的width时候，这个框就会很长，但是如果我限制了width那么这个option又显示不全，这个BUG仅仅会在IE中出现，如何解决呢，其实可以把select的下拉框用一个层覆盖掉，那个层会显示完整的数据，而select的widt指定好，这样整个页面的布局都不会被影响。所有的操作都通过JS实现，下面我就把代码贴出来。
function foo(px,py,pw,ph,baseElement,fid)
{
var win = document.getElementById(this.fid);
};
function dropdown_menu_hack(el)
{
if(el.runtimeStyle.behavior.toLowerCase()=="none"){return;}
el.runtimeStyle.behavior="none";
var ie5 = (document.namespaces==null);
el.ondblclick = function(e)
{
window.event.returnValue=false;
return false;
};
if(window.createPopup==null)
{
var fid = "dropdown_menu_hack_" + Date.parse(new Date());
window.createPopup = function()
{
if(window.createPopup.frameWindow==null)
{
el.insertAdjacentHTML("AfterEnd","<iframe id='"+fid+"' name='"+fid+"' src='about:blank' frameborder='1' scrolling='no'></></iframe>");
var f = document.frames[fid];
f.document.open();
f.document.write("<html><body></body></html>");
f.document.close();
f.fid = fid;
var fwin = document.getElementById(fid);
fwin.style.cssText="position:absolute;top:0;left:0;display:none;z-index:99999;";
f.show = function(px,py,pw,ph,baseElement)
{
py = py + baseElement.getBoundingClientRect().top + Math.max( document.body.scrollTop, document.documentElement.scrollTop) ;
px = px + baseElement.getBoundingClientRect().left + Math.max( document.body.scrollLeft, document.documentElement.scrollLeft) ;
fwin.style.width = pw + "px";
fwin.style.height = ph + "px";
fwin.style.posLeft =px ;
fwin.style.posTop = py ;
fwin.style.display="block";
};
f_hide = function(e)
{
if(window.event && window.event.srcElement && window.event.srcElement.tagName && window.event.srcElement.tagName.toLowerCase()=="select"){return true;}
fwin.style.display="none";
} ;
f.hide = f_hide;
document.attachEvent("onclick",f_hide);
document.attachEvent("onkeydown",f_hide);
}
return f;
};
}
function showMenu()
{
function selectMenu(obj,value)
{
var o = document.createElement("option");
o.value = value;
o.innerHTML = value;
while(el.options.length>0){el.options[0].removeNode(true);}
el.appendChild(o);
el.title = value;
el.contentIndex = value ;
el.value=value;
//alert(value);
//$("#deviceOwnerValue").val(value);
el.menu.hide();
}
el.menu.show(0 , el.offsetHeight , 10, 10, el);
var mb = el.menu.document.body;
mb.style.cssText ="border:solid 1px black;margin:0;padding:0;overflow-y:auto;overflow-x:auto;background:white;text-aligbn:center;FONT-WEIGHT: normal;FONT-SIZE: 8pt;COLOR: #003399;FONT-FAMILY: Arial;TEXT-DECORATION: none";
var t = el.contentHTML;
t = t.replace(/<select/gi,'<ul');
t = t.replace(/<option/gi,'<li');
t = t.replace(/<\/option/gi,'</li');
t = t.replace(/<\/select/gi,'</ul');
mb.innerHTML = t;
el.select = mb.all.tags("ul")[0];
el.select.style.cssText="list-style:none;margin:0;padding:0;";
mb.options = el.select.getElementsByTagName("li");
for(var i=0;i<mb.options.length;i++)
{
mb.options[i].selectedIndex = i;
mb.options[i].style.cssText = "list-style:none;margin:0;padding:1px 2px;width/**/:100%;cursor:hand;cursorointer;white-space:nowrap;FONT-WEIGHT: normal;FONT-SIZE: 8pt;COLOR: #003399;FONT-FAMILY: Arial;TEXT-DECORATION: none";
mb.options[i].title =mb.options[i].innerHTML;
mb.options[i].innerHTML =mb.options[i].innerHTML ;
mb.options[i].onmouseover = function()
{
if( mb.options.selected ){mb.options.selected.style.background="white";mb.options.selected.style.color="#003399";}
mb.options.selected = this;
this.style.background="#333366";this.style.color="white";
};
mb.options[i].onmouseout = function(){this.style.background="white";this.style.color="black";};
mb.options[i].onmousedown = function(){selectMenu(this,this.innerHTML);};
mb.options[i].onkeydown = function(){selectMenu(this,this.innerHTML);};
if(i == el.contentIndex)
{
mb.options[i].style.background="#333366";
mb.options[i].style.color="white";
mb.options.selected = mb.options[i];
}
}
var mw = Math.max( ( el.select.offsetWidth + 22 ), el.offsetWidth + 22 );
mw = Math.max( mw, ( mb.scrollWidth+22) );
var mh = mb.options.length * 15 + 8 ;
var mx = (ie5)?-3:0;
var my = el.offsetHeight -2;
var docH = document.documentElement.offsetHeight ;
var bottomH = docH - el.getBoundingClientRect().bottom ;
mh = Math.min(mh, Math.max(( docH - el.getBoundingClientRect().top - 50),100) );
if(( bottomH < mh) )
{
mh = Math.max( (bottomH - 12),10);
if( mh <100 )
{
my = -100 ;
}
mh = Math.max(mh,100);
}
self.focus();
el.menu.show( mx , my , mw, mh , el);
sync=null;
if(mb.options.selected)
{
mb.scrollTop = mb.options.selected.offsetTop;
}
window.onresize = function(){el.menu.hide()};
}
function switchMenu()
{
if(event.keyCode)
{
if(event.keyCode==40){ el.contentIndex++ ;}
else if(event.keyCode==38){ el.contentIndex--; }
}
else if(event.wheelDelta )
{
if (event.wheelDelta >= 120)
el.contentIndex++ ;
else if (event.wheelDelta <= -120)
el.contentIndex-- ;
}else{return true;}
if( el.contentIndex > (el.contentOptions.length-1) ){ el.contentIndex =0;}
else if (el.contentIndex<0){el.contentIndex = el.contentOptions.length-1 ;}
var o = document.createElement("option");
o.value = el.contentOptions[el.contentIndex].value;
o.innerHTML = el.contentOptions[el.contentIndex].text;
while(el.options.length>0){el.options[0].removeNode(true);}
el.appendChild(o);
el.title = o.innerHTML;
}
if(dropdown_menu_hack.menu ==null)
{
dropdown_menu_hack.menu = window.createPopup();
document.attachEvent("onkeydown",dropdown_menu_hack.menu.hide);
}
el.menu = dropdown_menu_hack.menu ;
el.contentOptions = new Array();
el.contentIndex = el.selectedIndex;
el.contentHTML = el.outerHTML;
for(var i=0;i<el.options.length;i++)
{
el.contentOptions [el.contentOptions.length] =
{
"value": el.options[i].value,
"text": el.options[i].innerHTML
};
if(!el.options[i].selected){el.options[i].removeNode(true);i--;};
}
el.onkeydown = switchMenu;
el.onclick = showMenu;
el.onmousewheel= switchMenu;
}
JS代码就是这些，在单击，下拉和鼠标滚轮操作时，响应相关的函数，在页面里面需要在需要这样用的元素中加入onfocus="window.dropdown_menu_hack(this)"这么一句就OK了，下面是代码，我用的struts2的标签，记得一定要用层将你要改的select包裹起来
<div id="pri">
<s:select name="deviceOwnedBy" id="deviceOwnedBy" list="deviceOwnedByList" listKey="value" listValue="value" headerKey="" headerValue="" cssClass="selectbox" style="width:150px;FONT-WEIGHT: normal;FONT-SIZE: 8pt;COLOR: #003399;FONT-FAMILY: Arial;TEXT-DECORATION: none" onfocus="window.dropdown_menu_hack(this)"></s:select>
</div>
