select option隐藏（兼容IE，firefox）

function search_sd_checkbox(selectId, searchText){
searchText = searchText || '';

var select = document.getElementById(selectId);
if(!select) return false;

var backupData = getOrCreateBackupData(select);

select.options.length = 0;
for(var i=0;i<backupData.length;i++){
var o = backupData[i];
if(o.text.toUpperCase().indexOf(searchText.toUpperCase())>-1)
select.options[select.options.length]=new Option(o.text,o.value);
}
}

function getOrCreateBackupData(select){
select = select || {};
return select.backupData || (function(s){
var ops = s.options;
var bkDatas = [];
for(var i=0;i<ops.length;i++)
bkDatas.push(new Option(ops[i].text, ops[i].value));
s.backupData = bkDatas;
return bkDatas;
})(select);
}