js 操作listbox

赋值

function select1()
    {
       var controlname=document.getElementById("ddgame");
       var name=document.getElementById("lboxgame");
       if(name.options.length>3)
       {alert('最多不能超过4项');return false;}
       var str=document.getElementById("lboxgame").value;      
       var t = controlname.options[controlname.selectedIndex].text;
       var v=controlname.options[controlname.selectedIndex].value;
       name.options.add(new Option(str+t,v));
      
    }

删除

function delete1()
    {
       var name=document.getElementById("lboxgame");
       name.options.remove(name.selectedIndex);
    }

得到值

function getvalue()
    {
       var name=document.getElementById("lboxgame");
       var str="";
       if(name.options.length==4)
       {
          for(var i=0;i<=3;i++)
          {
             if(str=="")
               str=name.options[i].value;
             else
             str=str+","+name.options[i].value;
          }
          document.getElementById("Hidden1").value=str;
       }
       else
       {alert('只能是4项');return false;}
      
    }