code: function digit(event) {
      var element = event.element
        , code = event.keyCode || event.which
        , result;
  
      result = (code >= 48 && code <= 57) || code === 8 || code === 46;
      if (!result) event.preventDefault();
  
      return {
        allowed: result,
        code: code,
        removal: code === 8 || code === 48
      };
    }
docs: Only allow numbers in the number field.
  
  @api private