How to avoid special characters using javascript

[Topper]

I am making one website for my client, I had completed the task what he asked from me, but on my meeting with him for showing the demonstration he asked me to insert the validation I told me fine. No problem!

Now the problem is the code of javascript for validation below is working correct, but while I am trying to avoid server round trips by using client side scripting. It is showing error for the especial charrater.

var eventName=document.getElementById("<%=txtEventName.ClientID%>").value;
 
 if (eventName=="")
      {
                 alert("Blank field");
                 document.getElementById("<%=txtEventName.ClientID%>").focus();
                 return false;
      }

Any one is with the solution to resolve this coding.

[Mammy]

var iChars = "!@#$%^&*()+=-[]\\\';,./{}|":<>?";
  for (var i = 0; i < document.formname.fieldname.value.length; i++) 
{
   if (iChars.indexOf(document.formname.fieldname.value.charAt(i)) != -1) 
{
   alert ("You are using special characters. \n Not allowed.\n Please do remove it and try again.");
   return false;
}
}

The above code will resolve your problem.