code: function ensureAnArray (arr) {
          if (Object.prototype.toString.call(arr) === '[object Array]') {
              return arr;
          } else if (arr === null || arr === void 0) {
              return [];
          } else {
              return [arr];
          }
      }
docs: return unchanged if array passed, otherwise wrap in an array
  @param  {Object|Array|Null} arr any object
  @return {Array}