index.js

(function (define) {
  define(function (require, exports, module) {
    'use strict';
    module.exports = function (value /*, ignoreSpecialCharacters */) {
      if (value === 0 || value === '') return true;

      if (!value || value === true) return false;

      var valueIsString = (typeof value === 'string');
      var ignoreSpecialCharacters = (arguments[1] === undefined);
      value = (valueIsString && ignoreSpecialCharacters)
        ? value.toLowerCase().replace(/[^\w]/gi, '')
        : value.toString();

      function test(candidate) {
        if (candidate.length < 2) return true;

        var size = candidate.length - 1;
        var first = candidate[0];
        var last = candidate[size];
        var remaining = candidate.slice(1, size);
        return (first === last)
          ? test(remaining)
          : false;
      }
      return test(value);
    };
  });
}(
  (typeof define == 'function' && define.amd)
    ? define
    : function (factory) { factory(require, exports, module); }
));