code: function(array, inter) {
        if (!_.isArray(array)) throw new TypeError;
        var sz = _.size(array);
        if (sz === 0) return array;
        if (sz === 1) return array;
  
        return slice.call(_.mapcat(array, function(elem) { 
          return _.cons(elem, [inter]);
        }), 0, -1);
      }
docs: Returns an array with some item between each element of a given array.