下拉列表框操作－－高级操作部分一

//全选列表中的项
function SelectAllOption(list)
{
for (var i=0; i<list.options.length; i++)
{
list.options[i].selected = true;
}
}

//反选列表中的项
function DeSelectOptions(list)
{
for (var i=0; i<list.options.length; i++)
{
list.options[i].selected = !list.options[i].selected;
}
}

//返回列表中选择项数目
function GetSelectedOptionsCnt(list)
{
var cnt = 0;
var i = 0;
for (i=0; i<list.options.length; i++)
{
if (list.options[i].selected)
{
cnt++;
}
}

return cnt;
}

//清空列表
function ClearList(list)
{
while (list.options.length > 0)
{
list.options[0] = null;
}
}

//删除列表选中项
//返回删除项的数量
function DelSelectedOptions(list)
{
var i = 0;
var deletedCnt = 0;
while (i < list.options.length)
{
if (list.options[i].selected)
{
list.options[i] = null;
deletedCnt++;
}
else
{
i++;
}
}

return deletedCnt;
}