phpjs/functions/var/is_null.js

php.js offers community built php functions in javascript

function is_null(mixed_var) {
  // From: http://phpjs.org/functions
  // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // *     example 1: is_null('23');
  // *     returns 1: false
  // *     example 2: is_null(null);
  // *     returns 2: true
  return (mixed_var === null);
}