Reading TextBox or other Control values with javascript

Reading TextBox or other Control values with javascript.
Assume TextBox ID="txtName"
First, there are the simple examples of a standard aspx page:

<script type="text/javascript" languague="javascript">
   function simple1() {
      var txtVal = $get('<%= txtName.ClientID %>').value;
   }
   function simple2() {
      var txtVal = $document.getElementById('<%= txtName.ClientID %>').value;
   }
</script>

Here is the complex sample used for accessing a MasterPage's updatePanel for example:

// In the ASPX class
private string scriptKey = "alertName";
private string script = "function alertName() { var txt = document.getElementById('[txtNameID]'); alert(txt.value); }"; 

// In the Page_Load event
script = script.Replace("[txtNameID]", txtName.ClientID);
ClientScript.RegisterClientScriptBlock(this.Page.GetType(), scriptKey, script, true); 

references: http://www.velocityreviews.com/forums/t109803-callback-manager-masterpage.html