谁能告诉我怎样用javascript控制下拉框的选项

Question

PropertiesaccessKey, className, dataFld, dataSrc, disabled, document, form, id, isTextEdit, lang, language, length, multiple, name, offsetHeight, offsetLeft, offsetParent, offsetTop, offsetWidth, outerHTML, outerText, parentElement, parentTextEdit, recordNumber, selectedIndex, size, sourceIndex, style, tabIndex, tagName, type, value Methodsadd, blur, click, contains, focus, getAttribute, insertAdjacentHTML, insertAdjacentText, item, remove, removeAttribute, scrollIntoView, setAttribute, tags Collectionsall, children, filters, options Eventsonafterupdate, onbeforeupdate, onblur, onchange, onclick, ondblclick, ondragstart, onerrorupdate, onfilterchange, onfocus, onhelp, onkeydown, onkeypress, onkeyup, onmousedown, onmousemove, onmouseout, onmouseover, onmouseup, onresize, onrowenter, onrowexit, onselectstart 添加项目了例子
<SELECT NAME="xx">
<option>asdsa</option>
</SELECT>
<script>
function add()
{
objxx=document.all['xx']
var oOption = document.createElement("OPTION");
oOption.text="Apples";
oOption.value="5";
objxx.add(oOption)
}
add()
</script>

Answer 1

上面的xx.options[i]下面有什么对象？

Answer 2

options是select的子对象集合
Property
    length 
Methods
    add, item, remove, tags 里面的元素都是option对象
Properties
    className, document, id, isTextEdit, language, offsetHeight, offsetParent, 
    offsetWidth, parentElement, parentTextEdit, selected, sourceIndex, style, 
    tagName, text, value 
Methods
    contains, getAttribute, removeAttribute, scrollIntoView, setAttribute 在你的计算机里查找htmlref.chm