AJAX级联下拉框的简单实现案例

send_request("GET","getClass.jsp?class1Id="+f.select11.value+"&class2Id=",null,"TEXT",populateClass2);
}
function doChange2() {
var f = document.forms[0];
send_request("GET","getClass.jsp?class1Id="+f.select11.value+"&class2Id="+f.select12.value,null,"TEXT",populateClass3);
}
function populateClass2(){
     var f=document.forms[0];
     if(http_request.readystate==4){
       if(http_request.status==200){
          var list=http_request.responseText;
          var classList=list.split("|");
          f.select12.options.length=1;
          for(var i=0;i<classList.length-1;i++){
            var temp=Trim(classList[i]).split(",");
            f.select12.add(new Option(temp[1],temp[0]));
          }
       }
     }
}

  function populateClass3(){
     var f=document.forms[0];
     if(http_request.readystate==4){
       if(http_request.status==200){
          var list=http_request.responseText;
          var classList=list.split("|");
          f.select13.options.length=1;
          for(var i=0;i<classList.length-1;i++){
            var temp=Trim(classList[i]).split(",");
            f.select13.add(new Option(temp[1],temp[0]));
          }
       }
     }
   }
   function LTrim(str)
{
    var whitespace = new String(" /t/n/r");
    var s = new String(str);
    if (whitespace.indexOf(s.charAt(0)) != -1)
    {
        var j=0, i = s.length;
        while (j < i && whitespace.indexOf(s.charAt(j)) != -1)
        {
            j++;
        }
        s = s.substring(j, i);
    }
    return s;
}
function RTrim(str)
{
    var whitespace = new String(" /t/n/r");
    var s = new String(str);