js问题

Question

window.onload=function() {
         var pro ="";
         var payFee1="";
         var num;
         var userid = document.getElementsByName("paidfee/USERID")[0].value;
     var sub = new HiddenSubmit("ACCT.bizBusiExpectPayFee.bizExpectPayFeeTaishouQuery");
     sub.add("T_AR_USERINFO/USERID",userid);
     sub.add("T_BL_COMMERADVANCERECORD/YRMONTH","");
     if(sub.submit()){
      num = sub.getProperty("list[@type='modify']/@rowNum");
        for(var i=0;i<num;i++){
         pro += sub.getProperty("list[@type='modify']/modify[@rowNum="+i+"]/yrmonth")+",";   
         var payFee = sub.getProperty("list[@type='modify']/modify[@rowNum="+i+"]/chrgsum");
         payFee1 += parseFloat(payFee).toFixed(2);
        }
         if(num>0){
          alert("该工商户"+pro+"预付费未缴，未缴总金额为￥"+payFee1+"");
         }
      }
       } 这个payFee 是个浮点型的，我想每次循环一次就把她相加起来，赋值给payFee1 ，现在的情况是payFee1 是个很长的字符串，数字并没有相加，有什么办法把他加起来没有捏？

Answer 1

var payFee1=0.0;  
payFee1 += parseFloat(payFee).toFixed(2); 
or payFee1 =  parseFloat(payFee1).toFixed(2) + parseFloat(payFee).toFixed(2);