code: function stringify(obj) {
      var cache = [];
  
      return JSON.stringify(obj, function (key, value) {
          if ((typeof value === 'undefined' ? 'undefined' : _typeof(value)) === 'object' && value !== null) {
              if (cache.indexOf(value) !== -1) {
                  return '[Circular]';
              }
              cache.push(value);
          }
          return value;
      });
  }
docs: Stringifies an object without the chance for circular error
  
  @param {Object} obj object to stringify
  @memberOf object
  @return {String} string form of the passed object