JS simple operation select and dropdownlist instances

This article illustrates how JS can easily operate select and dropdownlist. Share with you for your reference. The specific implementation method is as follows:

Js select server control select and dropdownlist

1. Js operation server control select

<select id="selectID" onchange="return showMessage()">

     <option value="0">== Please select a ==</option>

     <option value="1"> is </option>

     <option value="2"> no </option>

</select>


<script type="text/javascript" language="javascript">

  function showMessage() {

      if (document.getElementById("selectID").options[document.getElementById("selectID").selectedIndex].value == 1) {

   alert(" Hello, you chose no  1  a ");

   document.getElementById("txtContractName").setAttribute("enable",false);

      }

      else if (document.getElementById("selectID").options[document.getElementById("selectID").selectedIndex].value == 2) {

   alert(" Hello, you chose no  2  a ");

      }

  }

</script>
//Js operation server control dropdownlist

<asp:DropDownList ID="ddlFolder" runat="server" SkinID="ddlSkin" AutoPostBack="false" OnSelectedIndexChanged="ddlFolder_SelectedIndexChanged">    

        <asp:ListItem Value="0"> options 0</asp:ListItem>   

   <asp:ListItem Value="1"> options 1</asp:ListItem>  

</asp:DropDownList>    

<asp:DropDownList ID="ddlFolder" runat="server" SkinID="ddlSkin" AutoPostBack="false" OnSelectedIndexChanged="ddlFolder_SelectedIndexChanged"> 

  <asp:ListItem Value="0"> options 0</asp:ListItem>

  <asp:ListItem Value="1"> options 1</asp:ListItem> 

</asp:DropDownList>

JS code:

document.getElementById("ddlFolder").value="0";//0 For the item you want to select value

2. Select an item based on the Text value setting

var DropDownListCurrencyNew =  document.getElementById("ddlFolder");

for(i = 0; i < DropDownListCurrencyNew.options.length; i++)

{

          if(DropDownListCurrencyNew.options[i].text == " options 0")    

           {

               DropDownListCurrencyNew.options[i].selected = true; 

          }

}

Ii. Js reads the value and text of the selected item in DropDownList

Value:

var selValue = document.getElementById("DropDownList1").options[document.getElementById("DropDownList1").selectedIndex].value;

Text:

var selText = document.getElementById("DropDownList1").options[document.getElementById("DropDownList1").selectedIndex].text;