javascript双引号的问题

JScript code:
function doChange(){
var createdate=$f("acreatedate").value;
var serverdate= getcurrentdate();
checkDate(createdate,serverdate);
var url="ajaxAction.do?method=json&common=checkLog&classes=log.LogBo&createdate="+createdate;
new Ajax.AjaxRequest(url,doChangeRel,"",null,null);
}

function doChangeRel(){
var resonsetext=this.req.responseText;
//this.req.responseText=escape(resonsetext);
var rs = AnalysisJSON(this.req.responseText);
var createdate=$f("acreatedate").value;
var bcurdate = beforecurdate();
if(!rs){
return;
}
if(Datefirst(createdate,bcurdate)){
if(rs.resultSet.length==0){
alert("你不能选择过去的日期写新日志!");
clearFormByElements(logform,"acreatedate,atitle,acont");
return false;
}
}


if(rs.RETCODE != "0000"){
alert(rs.RETMSG);
return;
}else{
if(rs.resultSet.length > 0){

$f("atitle").value = rs.resultSet[0].title;
var reg=new RegExp("<br>","g");
var ac = rs.resultSet[0].cont;
ac = ac.replace(reg,"\r\n");//转换换行符
$f("acont").value = ac;