function is_int (mixed_var) {
  // http://kevin.vanzonneveld.net
  // +   original by: Alex
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +    revised by: Matt Bradley
  // +   bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +   improved by: WebDevHobo (http://webdevhobo.blogspot.com/)
  // +   improved by: Rafał Kukawski (http://blog.kukawski.pl)
  // %        note 1: 1.0 is simplified to 1 before it can be accessed by the function, this makes
  // %        note 1: it different from the PHP implementation. We can't fix this unfortunately.
  // *     example 1: is_int(23)
  // *     returns 1: true
  // *     example 2: is_int('23')
  // *     returns 2: false
  // *     example 3: is_int(23.5)
  // *     returns 3: false
  // *     example 4: is_int(true)
  // *     returns 4: false

  return mixed_var === +mixed_var && isFinite(mixed_var) && !(mixed_var % 1);
}

is_int(23)

true

is_int('23')

false

is_int(23.5)

false