My javascript code not working in mozilla firefox

This is my code for making textbox accept number only.

<asp:TextBox ID="txtRotationNo" runat="server" onkeydown="return NumberOnly();" CssClass="textbox"></asp:T开发者_开发知识库extBox>

function NumberOnly () {
    if(!(event.keyCode>=48 && event.keyCode<=57) && event.keyCode!=8) {
        event.returnValue=null;
    }
}

This code is working in Chrome and Opera, but not in firefox.

Can you tell me what's wrong with this code?

Many things wrong with the code, including the lack of an event argument, plus the wrong way about cancelling the event. Here, just replace the code with this:

function NumberOnly(e) {
  e = e || window.event; // remove this if you don't need IE support
  if (!(e.keyCode >= 48 && e.keyCode <= 57) && e.keyCode != 8)
    e.preventDefault();  // standard method of cancelling event
  return false;          // IE method of cancelling event
}

Firefox needs the event within the call of the handler and it needs to return "false" to ignore an action. This code might work:

function NumberOnly(event) {
  if(!(event.keyCode>=48 && event.keyCode<=57) && event.keyCode!=8) {
    event.returnValue=null;
    return false;
  }
}

But I think you can skip the event.returnValue=null;

On the contrary to IE, 'event' is not a global variable in Firefox. So you've got to pass the desired pressed key informations as an argument.

find the list of javascript validation function here,quite handy during development.

Thanks,

Ashish Chotalia