coding to validate textbox using javascript

function ValidText(evt,val)
      {
                  if (val.length>200)
                  return false;

         return true;
      }
in grid 

 <INPUT id="txtChar" onkeypress="return ValidText(event,this.value)" type="text" name="txtChar">

Refer to this similar CP question,

How to fix Character Length in a TextBox[^]

Hope it helps.

If you working with ASP.NET web controls, then TextBox have property called MaxLength. You can set that property to 200. You can find more information regarding MaxLength here[^]

Hi, call JS function on textbox. use below code for this:

<asp:textbox id="txtBox" runat="server" width="150px" onkeypress="javascript:return isValidateLen(this);" xmlns:asp="#unknown"> </asp:textbox>

JS Function

function isValidateLen(txtID)
{
txtObj = document.getElementById(txtID);
if(txtObj.value.length < 200)
{
return true;
}
else
{
return false;
}
}