javascript下拉循环if语句

我已经从8> 22:00开始创建了2个下拉菜单，但是在提交表单时，我要求我选择一个已经被警报选择并确认的开始时间选项我已经包括，真的困惑我！任何帮助赞赏。

I have created 2 drop down menus, from and to, these include times starting from 8 > 22:00, however on submitting the form it is asking me to select a start time which has already been selected and confirmed by an alert option i have included, has really confused me!! any help appreciated.

craig

window.status='Loading contingency scripts - please wait...';
audit('Loading contingency scripts');
var conting={ i:0

,start:function(){
window.status='Loading form - please wait...';
var t='';
t+='<form name="frm_conting" id="frm_conting" onsubmit="return false;">';
t+='<table width="100%" cellspacing="1" cellpadding="0">';
t+='<tr><td>Date (DD/MM/YY):</td><td><input type="text" size="8" value="'+current_date+'" id="date"></td></tr>';

t+='<tr><td>Time Started:</td><td><select id="timefrom"><option></option>';
  for(h=8;h<23;h++){  
      for(m=0;m<46;m=m+15){  t+='<option value='+nb[h]+':'+nb[m]+'>'+nb[h]+':'+nb[m]+'</option>';  };
     };
t+='</select></td></tr>';

t+='<tr><td>Time Finished:</td><td><select id="timefrom"><option></option>';
  for(h=8;h<23;h++){  
  for(m=0;m<46;m=m+15){  t+='<option value='+nb[h]+':'+nb[m]+'>'+nb[h]+':'+nb[m]+'</option>';  };
     };

t+='</select><tr><td>Extension #:</td><td><input type="text" size="5" value="'+my.extension+'" id="staffid"></td></tr>';
t+='<tr><td>Desk ID:</td><td><input type="text" size="5" value='+my.deskid+' id="desk"></td></tr>';
t+='<tr><td>Number of calls:</td><td><input type="text" size="5" id="calls"></td></tr>';
t+='<tr><td>Avid ID:</td><td><input type="text" size="5" id="avid"></td></tr>';
t+='<tr><td><input type="button" value="Submit" onClick="conting.save()"></td>'; 
t+='</table>';
t+='</form>';

div_form.innerHTML=t;  
window.resizeTo(400,385);
window.status='';
}


,save:function(){
 alert (frm_conting.timefrom.value);
  var conting_date=frm_conting.date.value; 
   if(!isdate(conting_date)){alert("You have entered an incorrect date.");return false;};

var conting_timefrom=frm_conting.timefrom.value;  
 if(isNaN(conting_timefrom)){alert("You need to enter a starting time.");return false;}; 
 if(conting_timefrom.value>conting_timeto.value){alert("The time you have entered is after the finish time.");return false;}; 

var conting_timeto=frm_conting.timeto.value; 
 if(isNaN(conting_timeto)){alert("You need to enter a finishing time.");return false;}; 
 if(conting_timeto.value<conting_timefrom.value){alert("The time you have entered is after the finish time.");return false;}; 

var conting_staffid=frm_conting.staffid.value; 
 if(conting_staffid.length!=5) { alert("You have entered an incorrect extension number.");return false;};

var conting_desk=frm_conting.desk.value; 
 if(conting_desk.length!=5) { alert("You have entered an incorrect desk ID.");return false;}; 

var conting_calls=frm_conting.calls.value; 
 if(isNaN(conting_calls)){alert("You have not entered amount of calls.");return false;};

var conting_avid=frm_conting.avid.value; 
 if(isNaN(conting_avid)){alert("You have entered an incorrect avid ID.");return false;};
 if(conting_avid.length!=5) { alert("You have entered an incorrect avid ID.");return false;}; 

 conn.open(db["contingency"]);
 rs.open("SELECT MAX(prac_id) FROM practice",conn);
var prac_id=rs.fields(0).value+1;
 rs.close();
 rs.open("INSERT INTO practice (prac_id, prac_staffid, prac_date, prac_timefrom, prac_timeto, prac_extension, prac_desk, prac_calls, prac_avid) VALUES (1, 2, 3, 4, 5, 6, 7, 8, 9)",conn); 
 conn.close();



}


};
 window.status='';

enter code here