Javascript numeric validation

Question

Numeric validation not working

 

function NumericOnly(event) {
//debugger;
      if (event.keyCode > 47 && event.keyCode < 58) {
            event.returnValue = true;
            return true;
      }
      else {
            event.returnValue = false;
            return false;
      }

}

suppose i entered a "v", it execute the else part but (event.returnVale=false;) value return to "v" i try some other options 

else {
      event.preventDefault();
      return false; 
     }

even i used like this 

   event.returnValue = null;

but my bad luck not working anyone know this help me...