code: function(arr, num) {
      if (isUndefined(num)) return arr[0];
      if (num < 0) num = 0;
      return arr.slice(0, num);
    }
docs: *
  @method first([num] = 1)
  @returns Mixed
  @short Returns the first element(s) in the array.
  @extra When `num` is passed, returns the first `num` elements in the array.
  
  @example
  
  [1,2,3].first()  -> 1
  [1,2,3].first(2) -> [1,2]
  
  @param {number} [num]
  
  *