javascirpt 客户端实现计算 TextBox DropDownLIst

function setSelectedValue(parUM)//设置dorpdownlist的选定值
{
    var ddlVUM='<%=FormView1.FindControl("DropDownList2").ClientID%>';
    var i=document.all(ddlVUM).options.length;
    var j;
    for(j=0;j<i;j++)
    {
      if(document.all(ddlVUM).options[j].text==parUM)
      document.all(ddlVUM).selectedIndex=j
      
    }
}

function Measurement()
{
  
    var txtLength= '<%=FormView1.FindControl("lengthTextBox").ClientID%>';
    var txtWidth= '<%=FormView1.FindControl("widthTextBox").ClientID%>';
    var txtHeight= '<%=FormView1.FindControl("heightTextBox").ClientID%>';
     var txtVolume= '<%=FormView1.FindControl("volumeTextBox").ClientID%>';
    var ddlUM='<%=FormView1.FindControl("DropDownList1").ClientID%>';
    var ddlVUM='<%=FormView1.FindControl("DropDownList2").ClientID%>';
   
    var Length=document.getElementById(txtLength).value;
    if(Length=='') Length=0;
    var Width=document.getElementById(txtWidth).value;
    if(Width=='') Width=0;
    var Height=document.getElementById(txtHeight).value;
    if(Height=='') Height=0;
   //var UM= document.all(ddlUM).selectedIndex;
    var UM=document.all(ddlUM).options[document.all(ddlUM).selectedIndex].text; 
    var VUM=document.getElementById(ddlVUM).innerText;
    var Volume;
  
    switch(UM)
    {
       case "M":
   Volume=Length*Width*Height;
   document.getElementById(txtVolume).innerText=Volume;
   setSelectedValue('CBM');
   break;
   
  case "CM":
   Volume=(Length/100)*(Width/100)*(Height/100);
   
   document.getElementById(txtVolume).innerText=Volume;
   setSelectedValue('CBM');
   break;
  case "IN":
   Volume=(Length/12)*(Width/12)*(Height/12);
   document.getElementById(txtVolume).innerText=Volume;
   setSelectedValue('CBFT');
   
   break;
   
  case "FT":
   Volume=Length*Width*Height;
   Volume=(Length/12)*(Width/12)*(Height/12);
   document.getElementById(txtVolume).innerText=Volume;
   setSelectedValue('CBFT');
   
  default:
  {
   Volume=Length*Width*Height;
   document.getElementById(txtVolume).innerText=Volume;
   setSelectedValue('CBM');
  }
  
    }

}