code: function Stringme(val, opt) {
  
      if (val === undefined) {
          val = '"undefined"';
      } else if (val === null) {
          val = '"null"';
      } else {
          var replace = opt && opt.replace ? opt.replace : null;
          var space = opt && opt.space ? opt.space : null;
          val = JSON.stringify(val, replace, space);
      }
  
      if (opt && opt.quotes === false && !/(^{|\[).*?([}\]])$/gm.test(val))
          val = val.slice(1, val.length - 1);
  
      return val;
  }
docs: Convert also undefined and null to string
  @param {*} val Anything you want stringify
  @param {object} [opt] Options
  @param {boolean} [opt.quotes=true] If false remove quotes
  @param {function|array|string|number} [opt.replace=null] Replace (JSON.stringify 2# param)
  @param {number|string} [opt.space=0] Space (JSON.stringify 3# param)
  @link https://developer.mozilla.org/it/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify
  @returns {string}
  @constructor