diff --git a/dist/__tests__/core/frame.js b/dist/__tests__/core/frame.js
index ffc4d4d..abc722a 100644
--- a/dist/__tests__/core/frame.js
+++ b/dist/__tests__/core/frame.js
@@ -384,12 +384,61 @@ describe('frame', function () {
           return "CREATEOBJECTURL";
         }
       };
-      // console.log(df.to_excel(new Workbook(), 'my test values', true));
+      df.to_excel(new _structs.Workbook(), 'my test values', true, { index: false });
 
       window.URL = originalURL;
     });
   });
 
+  describe('to_json', function () {
+    it('converts a pandas DataFrame to a json object when orient="columns"', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var dfJSON = df.to_json();
+      expect(dfJSON).toEqual({ x: { 0: 1, 1: 2, 2: 3 }, y: { 0: 2, 1: 3, 2: 4 } });
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="records"', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var dfJSON = df.to_json({ orient: 'records' });
+      expect(dfJSON).toBeInstanceOf(Array);
+      expect(dfJSON[0]).toEqual({ x: 1, y: 2 });
+      expect(dfJSON[1]).toEqual({ x: 2, y: 3 });
+      expect(dfJSON[2]).toEqual({ x: 3, y: 4 });
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="split"', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var dfJSON = df.to_json({ orient: 'split' });
+      expect(dfJSON).toBeInstanceOf(Object);
+      expect(dfJSON.columns).toEqual(['x', 'y']);
+      expect(dfJSON.index).toEqual([0, 1, 2]);
+      expect(dfJSON.values).toEqual([[1, 2], [2, 3], [3, 4]]);
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="index"', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var dfJSON = df.to_json({ orient: 'index' });
+      expect(dfJSON).toBeInstanceOf(Object);
+      expect(dfJSON).toEqual({
+        0: { x: 1, y: 2 },
+        1: { x: 2, y: 3 },
+        2: { x: 3, y: 4 }
+      });
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="values"', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var dfJSON = df.to_json({ orient: 'values' });
+      expect(dfJSON).toBeInstanceOf(Object);
+      expect(dfJSON).toEqual([[1, 2], [2, 3], [3, 4]]);
+    });
+  });
+
   describe('where', function () {
     it('checks for equality of a scalar and returns a DataFrame', function () {
       var df = new _frame2.default([{ x: 1, y: 2 }, { x: 2, y: 3 }]);
diff --git a/dist/__tests__/core/series.js b/dist/__tests__/core/series.js
index d8bb46f..a9d3fe1 100644
--- a/dist/__tests__/core/series.js
+++ b/dist/__tests__/core/series.js
@@ -594,5 +594,28 @@ describe('series', function () {
         }).toThrow();
       });
     });
+
+    describe('to_json', function () {
+      it('converts a pandas Series to a json object', function () {
+        var ds = new _series2.default([1, 2, 3, 4], { name: 'x' });
+
+        var dsJSON = ds.to_json();
+        expect(dsJSON).toEqual({ 0: 1, 1: 2, 2: 3, 3: 4 });
+      });
+
+      it('converts a pandas Series to a json object when orient="records"', function () {
+        var ds = new _series2.default([1, 2, 3, 4], { name: 'x' });
+
+        var dsJSON = ds.to_json({ orient: 'records' });
+        expect(dsJSON).toEqual([1, 2, 3, 4]);
+      });
+
+      it('converts a pandas Series to a json object when orient="split"', function () {
+        var ds = new _series2.default([1, 2, 3, 4], { name: 'x' });
+
+        var dsJSON = ds.to_json({ orient: 'split' });
+        expect(dsJSON).toEqual({ name: 'x', index: [0, 1, 2, 3], values: [1, 2, 3, 4] });
+      });
+    });
   });
 });
\ No newline at end of file
diff --git a/dist/core/frame.js b/dist/core/frame.js
index 2b7c807..232659e 100644
--- a/dist/core/frame.js
+++ b/dist/core/frame.js
@@ -138,19 +138,6 @@ var DataFrame = function (_NDFrame) {
       _this.set_axis(1, _immutable2.default.Seq.of());
     }
 
-    // TODO this is a slow operation
-    var valuesList = _immutable2.default.List([]);
-
-    var _loop = function _loop(idx) {
-      valuesList = valuesList.concat([_immutable2.default.List(_this.columns.map(function (k) {
-        return _this._data.get(k).iloc(idx);
-      }))]);
-    };
-
-    for (var idx = 0; idx < _this.length; idx += 1) {
-      _loop(idx);
-    }
-    _this._values = valuesList;
     _this._setup_axes(_immutable2.default.List.of(0, 1));
     return _this;
   }
@@ -594,6 +581,8 @@ var DataFrame = function (_NDFrame) {
      *    Name of values which will contain DataFrame
      * @param {boolean} download
      *    Download the excel file?
+     * @param {Object} kwargs
+     * @param {boolean} kwargs.index=true
      *
      * @return {Workbook}
      *
@@ -605,25 +594,41 @@ var DataFrame = function (_NDFrame) {
     key: 'to_excel',
     value: function to_excel(excel_writer) {
       var sheetName = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 'Sheet1';
+
+      var _this5 = this;
+
       var download = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : false;
+      var kwargs = arguments.length > 3 && arguments[3] !== undefined ? arguments[3] : { index: true };
 
       var wb = void 0;
-      if (excel_writer instanceof _structs.Workbook) {
-        var sheet = new _structs.Sheet(this.values);
 
+      var sheetObject = function sheetObject() {
+        if (kwargs.index) {
+          var colRow = _immutable2.default.List.of('').concat(_this5.columns.toList());
+          return new _structs.Sheet(_immutable2.default.List.of(colRow).concat(_this5.values.map(function (v, idx) {
+            return _immutable2.default.List.of(_this5.index.get(idx)).concat(v);
+          })));
+        }
+
+        return new _structs.Sheet(_immutable2.default.List.of(_this5.columns.toList()).concat(_this5.values));
+      };
+
+      if (excel_writer instanceof _structs.Workbook) {
         wb = excel_writer.copy();
-        wb.addSheet(sheetName, sheet);
+        wb.addSheet(sheetName, sheetObject());
       } else if (typeof excel_writer === 'string') {
         wb = new _structs.Workbook();
-        wb.addSheet(sheetName, new _structs.Sheet(this.values));
+        wb.addSheet(sheetName, sheetObject());
       } else throw new Error('excel_writer must be a file path or Workbook object');
 
       function s2ab(s) {
         var buf = new ArrayBuffer(s.length);
         var view = new Uint8Array(buf);
         for (var i = 0; i < s.length; i += 1) {
+          // noinspection Eslint
           view[i] = s.charCodeAt(i) & 0xFF;
-        }return buf;
+        }
+        return buf;
       }
 
       if (download) {
@@ -633,6 +638,89 @@ var DataFrame = function (_NDFrame) {
       return wb;
     }
 
+    /**
+     * Convert the DataFrame to a json object
+     *
+     * pandas equivalent: [DataFrame.to_json](http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.to_json.html)
+     *
+     * @param kwargs
+     * @param {string} [kwargs.orient=columns] orientation of JSON
+     *
+     * @returns {*}
+     *
+     * @example
+     * const df = new DataFrame([{x: 1, y: 2}, {x: 2, y: 3}, {x: 3, y: 4}]);
+     *
+     * // Returns {x: {0: 1, 1: 2, 2: 3}, y: {0: 1, 1: 2, 2: 3}}
+     * df.to_json();
+     *
+     * // Returns [{x: 1, y: 2}, {x: 2, y: 3}, {x: 3, y: 4}]
+     * df.to_json({orient: 'records'});
+     *
+     * // Returns {0: {x: 1, y: 2}, 1: {x: 2, y: 3}, 2: {x: 3, y: 4}}
+     * df.to_json({orient: 'index'});
+     *
+     * // Returns {index: [0, 1, 2], columns: ['x', 'y'], values: [[1, 2], [2, 3], [3, 4]]}
+     * df.to_json({orient: 'split'});
+     * 
+     * // Returns [[1, 2], [2, 3], [3, 4]]
+     * df.to_json({orient: 'values'});
+     */
+
+  }, {
+    key: 'to_json',
+    value: function to_json() {
+      var _this6 = this;
+
+      var kwargs = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : { orient: 'columns' };
+
+      var ALLOWED_ORIENT = ['records', 'split', 'index', 'values', 'columns'];
+      var orient = 'columns';
+
+      if (typeof kwargs.orient !== 'undefined') {
+        if (ALLOWED_ORIENT.indexOf(kwargs.orient) < 0) throw new TypeError('orient must be in ' + ALLOWED_ORIENT);
+        orient = kwargs.orient;
+      }
+
+      var json = void 0;
+      switch (orient) {
+        case 'records':
+          return this.values.map(function (row) {
+            var rowObj = {};
+            row.forEach(function (val, idx) {
+              rowObj[_this6.columns.get(idx)] = val;
+            });
+            return rowObj;
+          }).toArray();
+        case 'split':
+          return {
+            index: this.index.toArray(),
+            columns: this.columns.toArray(),
+            values: this.values.toJS()
+          };
+        case 'index':
+          json = {};
+          this.values.forEach(function (row, idx) {
+            var rowObj = {};
+            row.forEach(function (val, idx2) {
+              rowObj[_this6.columns.get(idx2)] = val;
+            });
+            json[_this6.index.get(idx)] = rowObj;
+          });
+          return json;
+        case 'values':
+          return this.values.toJS();
+        case 'columns':
+          json = {};
+          this.columns.forEach(function (c) {
+            json[c] = _this6.get(c).to_json({ orient: 'index' });
+          });
+          return json;
+        default:
+          throw new TypeError('orient must be in ' + ALLOWED_ORIENT);
+      }
+    }
+
     /**
      * Return the sum of the values in the `DataFrame` along the axis
      *
@@ -666,17 +754,17 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'sum',
     value: function sum() {
-      var _this5 = this;
+      var _this7 = this;
 
       var axis = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
 
       if (axis === 0) {
         return new _series2.default(this.columns.toArray().map(function (k) {
-          return _this5.get(k).sum();
+          return _this7.get(k).sum();
         }), { index: this.columns.toArray() });
       } else if (axis === 1) {
         return new _series2.default(_immutable2.default.Range(0, this.length).map(function (idx) {
-          return _this5.values.get(idx).reduce(function (s, k) {
+          return _this7.values.get(idx).reduce(function (s, k) {
             return s + k;
           }, 0);
         }).toList(), { index: this.index });
@@ -718,18 +806,18 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'mean',
     value: function mean() {
-      var _this6 = this;
+      var _this8 = this;
 
       var axis = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
 
       if (axis === 0) {
         return new _series2.default(this.columns.toArray().map(function (k) {
-          return _this6.get(k).mean();
+          return _this8.get(k).mean();
         }), { index: this.columns.toArray() });
       } else if (axis === 1) {
         return new _series2.default(_immutable2.default.Range(0, this.length).map(function (idx) {
-          return _this6.values.get(idx).reduce(function (s, k) {
-            return s + k / _this6.columns.size;
+          return _this8.values.get(idx).reduce(function (s, k) {
+            return s + k / _this8.columns.size;
           }, 0);
         }).toList(), { index: this.index });
       }
@@ -770,13 +858,13 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'std',
     value: function std() {
-      var _this7 = this;
+      var _this9 = this;
 
       var axis = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
 
       if (axis === 0) {
         return new _series2.default(this.columns.toArray().map(function (k) {
-          return _this7.get(k).std();
+          return _this9.get(k).std();
         }), { index: this.columns.toArray() });
       } else if (axis === 1) {
         return this.variance(axis).map(function (v) {
@@ -820,28 +908,28 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'variance',
     value: function variance() {
-      var _this8 = this;
+      var _this10 = this;
 
       var axis = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
 
       if (axis === 0) {
         return new _series2.default(this.columns.toArray().map(function (k) {
-          return _this8.get(k).variance();
+          return _this10.get(k).variance();
         }), { index: this.columns.toArray() });
       } else if (axis === 1) {
-        var _ret2 = function () {
-          var means = _this8.mean(axis).values;
+        var _ret = function () {
+          var means = _this10.mean(axis).values;
           return {
-            v: new _series2.default(_immutable2.default.Range(0, _this8.length).map(function (idx) {
-              return _this8.values.get(idx).reduce(function (s, k) {
+            v: new _series2.default(_immutable2.default.Range(0, _this10.length).map(function (idx) {
+              return _this10.values.get(idx).reduce(function (s, k) {
                 var diff = k - means.get(idx);
-                return s + diff * diff / (_this8.columns.size - 1);
+                return s + diff * diff / (_this10.columns.size - 1);
               }, 0);
-            }).toArray(), { index: _this8.index })
+            }).toArray(), { index: _this10.index })
           };
         }();
 
-        if ((typeof _ret2 === 'undefined' ? 'undefined' : (0, _typeof3.default)(_ret2)) === "object") return _ret2.v;
+        if ((typeof _ret === 'undefined' ? 'undefined' : (0, _typeof3.default)(_ret)) === "object") return _ret.v;
       }
 
       throw new _exceptions.InvalidAxisError();
@@ -948,7 +1036,7 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'diff',
     value: function diff() {
-      var _this9 = this;
+      var _this11 = this;
 
       var periods = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 1;
       var axis = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 0;
@@ -958,13 +1046,13 @@ var DataFrame = function (_NDFrame) {
 
       if (axis === 0) {
         return new DataFrame(_immutable2.default.Map(this.columns.map(function (k) {
-          return [k, _this9._data.get(k).diff(periods)];
+          return [k, _this11._data.get(k).diff(periods)];
         })), { index: this.index });
       } else if (axis === 1) {
         return new DataFrame(_immutable2.default.Map(this.columns.map(function (k, idx) {
-          if (idx < periods) return [k, new _series2.default(_immutable2.default.Repeat(null, _this9.length).toList(), { name: k, index: _this9.index })];
-          var compareCol = _this9.get(_this9.columns.get(idx - periods));
-          return [k, _this9.get(k).map(function (v, vIdx) {
+          if (idx < periods) return [k, new _series2.default(_immutable2.default.Repeat(null, _this11.length).toList(), { name: k, index: _this11.index })];
+          var compareCol = _this11.get(_this11.columns.get(idx - periods));
+          return [k, _this11.get(k).map(function (v, vIdx) {
             return v - compareCol.iloc(vIdx);
           })];
         })), { index: this.index });
@@ -999,7 +1087,7 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'pct_change',
     value: function pct_change() {
-      var _this10 = this;
+      var _this12 = this;
 
       var periods = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 1;
       var axis = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 0;
@@ -1009,13 +1097,13 @@ var DataFrame = function (_NDFrame) {
 
       if (axis === 0) {
         return new DataFrame(_immutable2.default.Map(this.columns.map(function (k) {
-          return [k, _this10._data.get(k).pct_change(periods)];
+          return [k, _this12._data.get(k).pct_change(periods)];
         })), { index: this.index });
       } else if (axis === 1) {
         return new DataFrame(_immutable2.default.Map(this.columns.map(function (k, idx) {
-          if (idx < periods) return [k, new _series2.default(_immutable2.default.Repeat(null, _this10.length).toList(), { name: k, index: _this10.index })];
-          var compareCol = _this10.get(_this10.columns.get(idx - periods));
-          return [k, _this10.get(k).map(function (v, vIdx) {
+          if (idx < periods) return [k, new _series2.default(_immutable2.default.Repeat(null, _this12.length).toList(), { name: k, index: _this12.index })];
+          var compareCol = _this12.get(_this12.columns.get(idx - periods));
+          return [k, _this12.get(k).map(function (v, vIdx) {
             return v / compareCol.iloc(vIdx) - 1;
           })];
         })), { index: this.index });
@@ -1083,18 +1171,18 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'pivot',
     value: function pivot(index, columns, values) {
-      var _this11 = this;
+      var _this13 = this;
 
       var uniqueVals = _immutable2.default.Map({});
       var uniqueCols = _immutable2.default.List([]);
 
       this.index.forEach(function (v, idx) {
-        var idxVal = _this11.get(index).iloc(idx);
-        var colVal = _this11.get(columns).iloc(idx);
+        var idxVal = _this13.get(index).iloc(idx);
+        var colVal = _this13.get(columns).iloc(idx);
 
         if (uniqueVals.hasIn([idxVal, colVal])) throw new Error('pivot index and column must be unique');
 
-        var val = _this11.get(values).iloc(idx);
+        var val = _this13.get(values).iloc(idx);
 
         uniqueVals = uniqueVals.setIn([idxVal, colVal], val);
         if (!uniqueCols.has(colVal)) uniqueCols = uniqueCols.push(colVal);
@@ -1113,6 +1201,23 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'values',
     get: function get() {
+      var _this14 = this;
+
+      if (this._values instanceof _immutable2.default.List) return (0, _get3.default)(DataFrame.prototype.__proto__ || Object.getPrototypeOf(DataFrame.prototype), 'values', this);
+
+      var valuesList = _immutable2.default.List([]);
+
+      var _loop = function _loop(idx) {
+        valuesList = valuesList.concat([_immutable2.default.List(_this14.columns.map(function (k) {
+          return _this14._data.get(k).iloc(idx);
+        }))]);
+      };
+
+      for (var idx = 0; idx < this.length; idx += 1) {
+        _loop(idx);
+      }
+      this._values = valuesList;
+
       return (0, _get3.default)(DataFrame.prototype.__proto__ || Object.getPrototypeOf(DataFrame.prototype), 'values', this);
     }
 
@@ -1153,14 +1258,14 @@ var DataFrame = function (_NDFrame) {
      */
     ,
     set: function set(columns) {
-      var _this12 = this;
+      var _this15 = this;
 
       if (!Array.isArray(columns) || columns.length !== this.columns.size) throw new Error('Columns must be array of same dimension');
 
       var nextData = {};
       columns.forEach(function (k, idx) {
-        var prevColumn = _this12.columns.get(idx);
-        var prevSeries = _this12.get(prevColumn);
+        var prevColumn = _this15.columns.get(idx);
+        var prevSeries = _this15.get(prevColumn);
 
         prevSeries.name = k;
         nextData[k] = prevSeries;
@@ -1205,7 +1310,7 @@ var DataFrame = function (_NDFrame) {
      */
     ,
     set: function set(index) {
-      var _this13 = this;
+      var _this16 = this;
 
       this.set_axis(0, (0, _utils.parseIndex)(index, this._data.get(this.columns.get(0)).values));
 
@@ -1216,7 +1321,7 @@ var DataFrame = function (_NDFrame) {
             v = _ref10[1];
 
         // noinspection Eslint
-        v.index = _this13.index;
+        v.index = _this16.index;
       });
     }
 
@@ -1237,10 +1342,10 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'length',
     get: function get() {
-      var _this14 = this;
+      var _this17 = this;
 
       return Math.max.apply(Math, (0, _toConsumableArray3.default)(this._data.keySeq().map(function (k) {
-        return _this14.get(k).length;
+        return _this17.get(k).length;
       }).toArray()));
     }
   }]);
diff --git a/dist/core/series.js b/dist/core/series.js
index a4fb591..6f35d52 100644
--- a/dist/core/series.js
+++ b/dist/core/series.js
@@ -1285,6 +1285,61 @@ var Series = function (_NDFrame) {
 
       return new Series(valueIndexMap.values, { name: this.name, index: valueIndexMap.index });
     }
+
+    /**
+     * Convert the Series to a json object
+     *
+     * pandas equivalent: [Series.to_json](http://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.to_json.html)
+     *
+     * @param kwargs
+     * @param {string} [kwargs.orient=columns] orientation of JSON
+     *
+     * @returns {*}
+     *
+     * @example
+     * const ds = new Series([1, 2, 3], {name: 'x'});
+     *
+     * // Returns {0: 1, 1: 2, 2: 3}
+     * ds.to_json();
+     *
+     * // Returns [1, 2, 3]
+     * ds.to_json({orient: 'records'});
+     *
+     * // Returns {index: [0, 1, 2], name: 'x', values: [1, 2, 3]}
+     * ds.to_json({orient: 'split'});
+     */
+
+  }, {
+    key: 'to_json',
+    value: function to_json() {
+      var _this9 = this;
+
+      var kwargs = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : { orient: 'index' };
+
+      var ALLOWED_ORIENT = ['records', 'split', 'index'];
+      var orient = 'index';
+
+      if (typeof kwargs.orient !== 'undefined') {
+        if (ALLOWED_ORIENT.indexOf(kwargs.orient) < 0) throw new TypeError('orient must be in ' + ALLOWED_ORIENT);
+        orient = kwargs.orient;
+      }
+
+      var json = void 0;
+      switch (orient) {
+        case 'records':
+          return this.values.toArray();
+        case 'split':
+          return { index: this.index.toArray(), name: this.name, values: this.values.toJS() };
+        case 'index':
+          json = {};
+          this.values.forEach(function (v, idx) {
+            json[_this9.index.get(idx)] = v;
+          });
+          return json;
+        default:
+          throw new TypeError('orient must be in ' + ALLOWED_ORIENT);
+      }
+    }
   }, {
     key: 'kwargs',
     get: function get() {
diff --git a/dist/core/structs.js b/dist/core/structs.js
index 53fa6aa..3c193c5 100644
--- a/dist/core/structs.js
+++ b/dist/core/structs.js
@@ -77,6 +77,7 @@ var Workbook = exports.Workbook = function () {
   }, {
     key: 'addSheet',
     value: function addSheet(sheetName, sheetContent) {
+      console.log(sheetContent.values);
       this._sheets.addSheet(sheetName, sheetContent);
     }
   }, {
diff --git a/package.json b/package.json
index 8df5eab..cc14832 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "pandas-js",
-  "version": "0.1.16",
+  "version": "0.1.17",
   "description": "Pandas for JavaScript",
   "author": "StratoDem Analytics tech@stratodem.com",
   "contributors": [
diff --git a/src/es6/__tests__/core/frame.js b/src/es6/__tests__/core/frame.js
index 74b470c..23a7523 100644
--- a/src/es6/__tests__/core/frame.js
+++ b/src/es6/__tests__/core/frame.js
@@ -339,12 +339,61 @@ describe('frame', () => {
       window.URL = {
         createObjectURL: (blob) => { return "CREATEOBJECTURL"; },
       };
-      // console.log(df.to_excel(new Workbook(), 'my test values', true));
+      df.to_excel(new Workbook(), 'my test values', true, {index: false});
 
       window.URL = originalURL;
     });
   });
 
+  describe('to_json', () => {
+    it('converts a pandas DataFrame to a json object when orient="columns"', () => {
+      const df = new DataFrame(Immutable.Map({x: new Series([1, 2, 3]), y: new Series([2, 3, 4])}));
+
+      const dfJSON = df.to_json();
+      expect(dfJSON).toEqual({x: {0: 1, 1: 2, 2: 3}, y: {0: 2, 1: 3, 2: 4}});
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="records"', () => {
+      const df = new DataFrame(Immutable.Map({x: new Series([1, 2, 3]), y: new Series([2, 3, 4])}));
+
+      const dfJSON = df.to_json({orient: 'records'});
+      expect(dfJSON).toBeInstanceOf(Array);
+      expect(dfJSON[0]).toEqual({x: 1, y: 2});
+      expect(dfJSON[1]).toEqual({x: 2, y: 3});
+      expect(dfJSON[2]).toEqual({x: 3, y: 4});
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="split"', () => {
+      const df = new DataFrame(Immutable.Map({x: new Series([1, 2, 3]), y: new Series([2, 3, 4])}));
+
+      const dfJSON = df.to_json({orient: 'split'});
+      expect(dfJSON).toBeInstanceOf(Object);
+      expect(dfJSON.columns).toEqual(['x', 'y']);
+      expect(dfJSON.index).toEqual([0, 1, 2]);
+      expect(dfJSON.values).toEqual([[1, 2], [2, 3], [3, 4]]);
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="index"', () => {
+      const df = new DataFrame(Immutable.Map({x: new Series([1, 2, 3]), y: new Series([2, 3, 4])}));
+
+      const dfJSON = df.to_json({orient: 'index'});
+      expect(dfJSON).toBeInstanceOf(Object);
+      expect(dfJSON).toEqual({
+        0: {x: 1, y: 2},
+        1: {x: 2, y: 3},
+        2: {x: 3, y: 4},
+      });
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="values"', () => {
+      const df = new DataFrame(Immutable.Map({x: new Series([1, 2, 3]), y: new Series([2, 3, 4])}));
+
+      const dfJSON = df.to_json({orient: 'values'});
+      expect(dfJSON).toBeInstanceOf(Object);
+      expect(dfJSON).toEqual([[1, 2], [2, 3], [3, 4]]);
+    });
+  });
+
   describe('where', () => {
     it('checks for equality of a scalar and returns a DataFrame', () => {
       const df = new DataFrame([{x: 1, y: 2}, {x: 2, y: 3}]);
diff --git a/src/es6/__tests__/core/series.js b/src/es6/__tests__/core/series.js
index 4b292d3..96e6829 100644
--- a/src/es6/__tests__/core/series.js
+++ b/src/es6/__tests__/core/series.js
@@ -565,5 +565,28 @@ describe('series', () => {
         expect(() => { ds1.corr(ds2); }).toThrow();
       });
     });
+
+    describe('to_json', () => {
+      it('converts a pandas Series to a json object', () => {
+        const ds = new Series([1, 2, 3, 4], {name: 'x'});
+
+        const dsJSON = ds.to_json();
+        expect(dsJSON).toEqual({0: 1, 1: 2, 2: 3, 3: 4});
+      });
+
+      it('converts a pandas Series to a json object when orient="records"', () => {
+        const ds = new Series([1, 2, 3, 4], {name: 'x'});
+
+        const dsJSON = ds.to_json({orient: 'records'});
+        expect(dsJSON).toEqual([1, 2, 3, 4]);
+      });
+
+      it('converts a pandas Series to a json object when orient="split"', () => {
+        const ds = new Series([1, 2, 3, 4], {name: 'x'});
+
+        const dsJSON = ds.to_json({orient: 'split'});
+        expect(dsJSON).toEqual({name: 'x', index: [0, 1, 2, 3], values: [1, 2, 3, 4]});
+      });
+    });
   });
 });
diff --git a/src/es6/core/frame.js b/src/es6/core/frame.js
index 3b048a3..3761f2f 100644
--- a/src/es6/core/frame.js
+++ b/src/es6/core/frame.js
@@ -14,7 +14,7 @@ const parseArrayToSeriesMap = (array, index) => {
 
   array.forEach((el) => {
     if (el instanceof Immutable.Map) {
-      el.keySeq().forEach(k => {
+      el.keySeq().forEach((k) => {
         if (dataMap.has(k)) {
           dataMap = dataMap.set(k, dataMap.get(k).push(el.get(k)));
         } else {
@@ -32,7 +32,7 @@ const parseArrayToSeriesMap = (array, index) => {
     }
   });
 
-  dataMap.keySeq().forEach(k => {
+  dataMap.keySeq().forEach((k) => {
     dataMap = dataMap.set(k, new Series(dataMap.get(k), {name: k, index}));
   });
 
@@ -84,13 +84,6 @@ export default class DataFrame extends NDFrame {
       this.set_axis(1, Immutable.Seq.of());
     }
 
-    // TODO this is a slow operation
-    let valuesList = Immutable.List([]);
-    for (let idx = 0; idx < this.length; idx += 1) {
-      valuesList = valuesList.concat(
-        [Immutable.List(this.columns.map(k => this._data.get(k).iloc(idx)))]);
-    }
-    this._values = valuesList;
     this._setup_axes(Immutable.List.of(0, 1));
   }
 
@@ -188,6 +181,16 @@ export default class DataFrame extends NDFrame {
    * df.values;
    */
   get values() {
+    if (this._values instanceof Immutable.List)
+      return super.values;
+
+    let valuesList = Immutable.List([]);
+    for (let idx = 0; idx < this.length; idx += 1) {
+      valuesList = valuesList.concat(
+        [Immutable.List(this.columns.map(k => this._data.get(k).iloc(idx)))]);
+    }
+    this._values = valuesList;
+
     return super.values;
   }
 
@@ -573,28 +576,42 @@ export default class DataFrame extends NDFrame {
    *    Name of values which will contain DataFrame
    * @param {boolean} download
    *    Download the excel file?
+   * @param {Object} kwargs
+   * @param {boolean} kwargs.index=true
    *
    * @return {Workbook}
    *
    * @example
    *
    */
-  to_excel(excel_writer, sheetName = 'Sheet1', download = false) {
+  to_excel(excel_writer, sheetName = 'Sheet1', download = false, kwargs = {index: true}) {
     let wb;
-    if (excel_writer instanceof Workbook) {
-      const sheet = new Sheet(this.values);
 
+    const sheetObject = () => {
+      if (kwargs.index) {
+        const colRow = Immutable.List.of('').concat(this.columns.toList());
+        return new Sheet(
+          Immutable.List.of(colRow)
+            .concat(this.values.map((v, idx) => Immutable.List.of(this.index.get(idx)).concat(v))));
+      }
+
+      return new Sheet(Immutable.List.of(this.columns.toList()).concat(this.values));
+    };
+
+    if (excel_writer instanceof Workbook) {
       wb = excel_writer.copy();
-      wb.addSheet(sheetName, sheet);
+      wb.addSheet(sheetName, sheetObject());
     } else if (typeof excel_writer === 'string') {
       wb = new Workbook();
-      wb.addSheet(sheetName, new Sheet(this.values));
+      wb.addSheet(sheetName, sheetObject());
     } else throw new Error('excel_writer must be a file path or Workbook object');
 
     function s2ab(s) {
       const buf = new ArrayBuffer(s.length);
       const view = new Uint8Array(buf);
-      for (let i = 0; i < s.length; i += 1) view[i] = s.charCodeAt(i) & 0xFF;
+      for (let i = 0; i < s.length; i += 1) { // noinspection Eslint
+        view[i] = s.charCodeAt(i) & 0xFF;
+      }
       return buf;
     }
 
@@ -607,6 +624,79 @@ export default class DataFrame extends NDFrame {
     return wb;
   }
 
+  /**
+   * Convert the DataFrame to a json object
+   *
+   * pandas equivalent: [DataFrame.to_json](http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.to_json.html)
+   *
+   * @param kwargs
+   * @param {string} [kwargs.orient=columns] orientation of JSON
+   *
+   * @returns {*}
+   *
+   * @example
+   * const df = new DataFrame([{x: 1, y: 2}, {x: 2, y: 3}, {x: 3, y: 4}]);
+   *
+   * // Returns {x: {0: 1, 1: 2, 2: 3}, y: {0: 1, 1: 2, 2: 3}}
+   * df.to_json();
+   *
+   * // Returns [{x: 1, y: 2}, {x: 2, y: 3}, {x: 3, y: 4}]
+   * df.to_json({orient: 'records'});
+   *
+   * // Returns {0: {x: 1, y: 2}, 1: {x: 2, y: 3}, 2: {x: 3, y: 4}}
+   * df.to_json({orient: 'index'});
+   *
+   * // Returns {index: [0, 1, 2], columns: ['x', 'y'], values: [[1, 2], [2, 3], [3, 4]]}
+   * df.to_json({orient: 'split'});
+   * 
+   * // Returns [[1, 2], [2, 3], [3, 4]]
+   * df.to_json({orient: 'values'});
+   */
+  to_json(kwargs = {orient: 'columns'}) {
+    const ALLOWED_ORIENT = ['records', 'split', 'index', 'values', 'columns'];
+    let orient = 'columns';
+
+    if (typeof kwargs.orient !== 'undefined') {
+      if (ALLOWED_ORIENT.indexOf(kwargs.orient) < 0)
+        throw new TypeError(`orient must be in ${ALLOWED_ORIENT}`);
+      orient = kwargs.orient;
+    }
+
+    let json;
+    switch (orient) {
+      case 'records':
+        return this.values.map((row) => {
+          const rowObj = {};
+          row.forEach((val, idx) => { rowObj[this.columns.get(idx)] = val; });
+          return rowObj;
+        }).toArray();
+      case 'split':
+        return {
+          index: this.index.toArray(),
+          columns: this.columns.toArray(),
+          values: this.values.toJS(),
+        };
+      case 'index':
+        json = {};
+        this.values.forEach((row, idx) => {
+          const rowObj = {};
+          row.forEach((val, idx2) => { rowObj[this.columns.get(idx2)] = val; });
+          json[this.index.get(idx)] = rowObj;
+        });
+        return json;
+      case 'values':
+        return this.values.toJS();
+      case 'columns':
+        json = {};
+        this.columns.forEach((c) => {
+          json[c] = this.get(c).to_json({orient: 'index'});
+        });
+        return json;
+      default:
+        throw new TypeError(`orient must be in ${ALLOWED_ORIENT}`);
+    }
+  }
+
   /**
    * Return the sum of the values in the `DataFrame` along the axis
    *
diff --git a/src/es6/core/series.js b/src/es6/core/series.js
index b980f26..8fb374e 100644
--- a/src/es6/core/series.js
+++ b/src/es6/core/series.js
@@ -1158,4 +1158,53 @@ export default class Series extends NDFrame {
 
     return new Series(valueIndexMap.values, {name: this.name, index: valueIndexMap.index});
   }
+
+  /**
+   * Convert the Series to a json object
+   *
+   * pandas equivalent: [Series.to_json](http://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.to_json.html)
+   *
+   * @param kwargs
+   * @param {string} [kwargs.orient=columns] orientation of JSON
+   *
+   * @returns {*}
+   *
+   * @example
+   * const ds = new Series([1, 2, 3], {name: 'x'});
+   *
+   * // Returns {0: 1, 1: 2, 2: 3}
+   * ds.to_json();
+   *
+   * // Returns [1, 2, 3]
+   * ds.to_json({orient: 'records'});
+   *
+   * // Returns {index: [0, 1, 2], name: 'x', values: [1, 2, 3]}
+   * ds.to_json({orient: 'split'});
+   */
+  to_json(kwargs = {orient: 'index'}) {
+    const ALLOWED_ORIENT = ['records', 'split', 'index'];
+    let orient = 'index';
+
+    if (typeof kwargs.orient !== 'undefined') {
+      if (ALLOWED_ORIENT.indexOf(kwargs.orient) < 0)
+        throw new TypeError(`orient must be in ${ALLOWED_ORIENT}`);
+      orient = kwargs.orient;
+    }
+
+    let json;
+    switch (orient) {
+      case 'records':
+        return this.values.toArray();
+      case 'split':
+        return {index: this.index.toArray(), name: this.name, values: this.values.toJS()};
+      case 'index':
+        json = {};
+        this.values.forEach((v, idx) => {
+          json[this.index.get(idx)] = v;
+        });
+        return json;
+      default:
+        throw new TypeError(`orient must be in ${ALLOWED_ORIENT}`);
+    }
+  }
 }
diff --git a/src/es6/core/structs.js b/src/es6/core/structs.js
index ad32577..8652437 100644
--- a/src/es6/core/structs.js
+++ b/src/es6/core/structs.js
@@ -55,6 +55,7 @@ export class Workbook {
    * @param {Sheet} sheetContent
    */
   addSheet(sheetName, sheetContent) {
+    console.log(sheetContent.values);
     this._sheets.addSheet(sheetName, sheetContent);
   }
 
diff --git a/src/js/__tests__/core/frame.js b/src/js/__tests__/core/frame.js
index 9fa2ebe..a97ebf0 100644
--- a/src/js/__tests__/core/frame.js
+++ b/src/js/__tests__/core/frame.js
@@ -384,12 +384,61 @@ describe('frame', function () {
           return "CREATEOBJECTURL";
         }
       };
-      // console.log(df.to_excel(new Workbook(), 'my test values', true));
+      df.to_excel(new _structs.Workbook(), 'my test values', true, { index: false });
 
       window.URL = originalURL;
     });
   });
 
+  describe('to_json', function () {
+    it('converts a pandas DataFrame to a json object when orient="columns"', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var dfJSON = df.to_json();
+      expect(dfJSON).toEqual({ x: { 0: 1, 1: 2, 2: 3 }, y: { 0: 2, 1: 3, 2: 4 } });
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="records"', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var dfJSON = df.to_json({ orient: 'records' });
+      expect(dfJSON).toBeInstanceOf(Array);
+      expect(dfJSON[0]).toEqual({ x: 1, y: 2 });
+      expect(dfJSON[1]).toEqual({ x: 2, y: 3 });
+      expect(dfJSON[2]).toEqual({ x: 3, y: 4 });
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="split"', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var dfJSON = df.to_json({ orient: 'split' });
+      expect(dfJSON).toBeInstanceOf(Object);
+      expect(dfJSON.columns).toEqual(['x', 'y']);
+      expect(dfJSON.index).toEqual([0, 1, 2]);
+      expect(dfJSON.values).toEqual([[1, 2], [2, 3], [3, 4]]);
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="index"', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var dfJSON = df.to_json({ orient: 'index' });
+      expect(dfJSON).toBeInstanceOf(Object);
+      expect(dfJSON).toEqual({
+        0: { x: 1, y: 2 },
+        1: { x: 2, y: 3 },
+        2: { x: 3, y: 4 }
+      });
+    });
+
+    it('converts a pandas DataFrame to a json object when orient="values"', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var dfJSON = df.to_json({ orient: 'values' });
+      expect(dfJSON).toBeInstanceOf(Object);
+      expect(dfJSON).toEqual([[1, 2], [2, 3], [3, 4]]);
+    });
+  });
+
   describe('where', function () {
     it('checks for equality of a scalar and returns a DataFrame', function () {
       var df = new _frame2.default([{ x: 1, y: 2 }, { x: 2, y: 3 }]);
diff --git a/src/js/__tests__/core/series.js b/src/js/__tests__/core/series.js
index 7dd8387..7d59818 100644
--- a/src/js/__tests__/core/series.js
+++ b/src/js/__tests__/core/series.js
@@ -594,5 +594,28 @@ describe('series', function () {
         }).toThrow();
       });
     });
+
+    describe('to_json', function () {
+      it('converts a pandas Series to a json object', function () {
+        var ds = new _series2.default([1, 2, 3, 4], { name: 'x' });
+
+        var dsJSON = ds.to_json();
+        expect(dsJSON).toEqual({ 0: 1, 1: 2, 2: 3, 3: 4 });
+      });
+
+      it('converts a pandas Series to a json object when orient="records"', function () {
+        var ds = new _series2.default([1, 2, 3, 4], { name: 'x' });
+
+        var dsJSON = ds.to_json({ orient: 'records' });
+        expect(dsJSON).toEqual([1, 2, 3, 4]);
+      });
+
+      it('converts a pandas Series to a json object when orient="split"', function () {
+        var ds = new _series2.default([1, 2, 3, 4], { name: 'x' });
+
+        var dsJSON = ds.to_json({ orient: 'split' });
+        expect(dsJSON).toEqual({ name: 'x', index: [0, 1, 2, 3], values: [1, 2, 3, 4] });
+      });
+    });
   });
 });
diff --git a/src/js/core/frame.js b/src/js/core/frame.js
index a84c76f..c85fef6 100644
--- a/src/js/core/frame.js
+++ b/src/js/core/frame.js
@@ -138,19 +138,6 @@ var DataFrame = function (_NDFrame) {
       _this.set_axis(1, _immutable2.default.Seq.of());
     }
 
-    // TODO this is a slow operation
-    var valuesList = _immutable2.default.List([]);
-
-    var _loop = function _loop(idx) {
-      valuesList = valuesList.concat([_immutable2.default.List(_this.columns.map(function (k) {
-        return _this._data.get(k).iloc(idx);
-      }))]);
-    };
-
-    for (var idx = 0; idx < _this.length; idx += 1) {
-      _loop(idx);
-    }
-    _this._values = valuesList;
     _this._setup_axes(_immutable2.default.List.of(0, 1));
     return _this;
   }
@@ -594,6 +581,8 @@ var DataFrame = function (_NDFrame) {
      *    Name of values which will contain DataFrame
      * @param {boolean} download
      *    Download the excel file?
+     * @param {Object} kwargs
+     * @param {boolean} kwargs.index=true
      *
      * @return {Workbook}
      *
@@ -605,25 +594,41 @@ var DataFrame = function (_NDFrame) {
     key: 'to_excel',
     value: function to_excel(excel_writer) {
       var sheetName = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 'Sheet1';
+
+      var _this5 = this;
+
       var download = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : false;
+      var kwargs = arguments.length > 3 && arguments[3] !== undefined ? arguments[3] : { index: true };
 
       var wb = void 0;
-      if (excel_writer instanceof _structs.Workbook) {
-        var sheet = new _structs.Sheet(this.values);
 
+      var sheetObject = function sheetObject() {
+        if (kwargs.index) {
+          var colRow = _immutable2.default.List.of('').concat(_this5.columns.toList());
+          return new _structs.Sheet(_immutable2.default.List.of(colRow).concat(_this5.values.map(function (v, idx) {
+            return _immutable2.default.List.of(_this5.index.get(idx)).concat(v);
+          })));
+        }
+
+        return new _structs.Sheet(_immutable2.default.List.of(_this5.columns.toList()).concat(_this5.values));
+      };
+
+      if (excel_writer instanceof _structs.Workbook) {
         wb = excel_writer.copy();
-        wb.addSheet(sheetName, sheet);
+        wb.addSheet(sheetName, sheetObject());
       } else if (typeof excel_writer === 'string') {
         wb = new _structs.Workbook();
-        wb.addSheet(sheetName, new _structs.Sheet(this.values));
+        wb.addSheet(sheetName, sheetObject());
       } else throw new Error('excel_writer must be a file path or Workbook object');
 
       function s2ab(s) {
         var buf = new ArrayBuffer(s.length);
         var view = new Uint8Array(buf);
         for (var i = 0; i < s.length; i += 1) {
+          // noinspection Eslint
           view[i] = s.charCodeAt(i) & 0xFF;
-        }return buf;
+        }
+        return buf;
       }
 
       if (download) {
@@ -633,6 +638,89 @@ var DataFrame = function (_NDFrame) {
       return wb;
     }
 
+    /**
+     * Convert the DataFrame to a json object
+     *
+     * pandas equivalent: [DataFrame.to_json](http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.to_json.html)
+     *
+     * @param kwargs
+     * @param {string} [kwargs.orient=columns] orientation of JSON
+     *
+     * @returns {*}
+     *
+     * @example
+     * const df = new DataFrame([{x: 1, y: 2}, {x: 2, y: 3}, {x: 3, y: 4}]);
+     *
+     * // Returns {x: {0: 1, 1: 2, 2: 3}, y: {0: 1, 1: 2, 2: 3}}
+     * df.to_json();
+     *
+     * // Returns [{x: 1, y: 2}, {x: 2, y: 3}, {x: 3, y: 4}]
+     * df.to_json({orient: 'records'});
+     *
+     * // Returns {0: {x: 1, y: 2}, 1: {x: 2, y: 3}, 2: {x: 3, y: 4}}
+     * df.to_json({orient: 'index'});
+     *
+     * // Returns {index: [0, 1, 2], columns: ['x', 'y'], values: [[1, 2], [2, 3], [3, 4]]}
+     * df.to_json({orient: 'split'});
+     * 
+     * // Returns [[1, 2], [2, 3], [3, 4]]
+     * df.to_json({orient: 'values'});
+     */
+
+  }, {
+    key: 'to_json',
+    value: function to_json() {
+      var _this6 = this;
+
+      var kwargs = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : { orient: 'columns' };
+
+      var ALLOWED_ORIENT = ['records', 'split', 'index', 'values', 'columns'];
+      var orient = 'columns';
+
+      if (typeof kwargs.orient !== 'undefined') {
+        if (ALLOWED_ORIENT.indexOf(kwargs.orient) < 0) throw new TypeError('orient must be in ' + ALLOWED_ORIENT);
+        orient = kwargs.orient;
+      }
+
+      var json = void 0;
+      switch (orient) {
+        case 'records':
+          return this.values.map(function (row) {
+            var rowObj = {};
+            row.forEach(function (val, idx) {
+              rowObj[_this6.columns.get(idx)] = val;
+            });
+            return rowObj;
+          }).toArray();
+        case 'split':
+          return {
+            index: this.index.toArray(),
+            columns: this.columns.toArray(),
+            values: this.values.toJS()
+          };
+        case 'index':
+          json = {};
+          this.values.forEach(function (row, idx) {
+            var rowObj = {};
+            row.forEach(function (val, idx2) {
+              rowObj[_this6.columns.get(idx2)] = val;
+            });
+            json[_this6.index.get(idx)] = rowObj;
+          });
+          return json;
+        case 'values':
+          return this.values.toJS();
+        case 'columns':
+          json = {};
+          this.columns.forEach(function (c) {
+            json[c] = _this6.get(c).to_json({ orient: 'index' });
+          });
+          return json;
+        default:
+          throw new TypeError('orient must be in ' + ALLOWED_ORIENT);
+      }
+    }
+
     /**
      * Return the sum of the values in the `DataFrame` along the axis
      *
@@ -666,17 +754,17 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'sum',
     value: function sum() {
-      var _this5 = this;
+      var _this7 = this;
 
       var axis = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
 
       if (axis === 0) {
         return new _series2.default(this.columns.toArray().map(function (k) {
-          return _this5.get(k).sum();
+          return _this7.get(k).sum();
         }), { index: this.columns.toArray() });
       } else if (axis === 1) {
         return new _series2.default(_immutable2.default.Range(0, this.length).map(function (idx) {
-          return _this5.values.get(idx).reduce(function (s, k) {
+          return _this7.values.get(idx).reduce(function (s, k) {
             return s + k;
           }, 0);
         }).toList(), { index: this.index });
@@ -718,18 +806,18 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'mean',
     value: function mean() {
-      var _this6 = this;
+      var _this8 = this;
 
       var axis = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
 
       if (axis === 0) {
         return new _series2.default(this.columns.toArray().map(function (k) {
-          return _this6.get(k).mean();
+          return _this8.get(k).mean();
         }), { index: this.columns.toArray() });
       } else if (axis === 1) {
         return new _series2.default(_immutable2.default.Range(0, this.length).map(function (idx) {
-          return _this6.values.get(idx).reduce(function (s, k) {
-            return s + k / _this6.columns.size;
+          return _this8.values.get(idx).reduce(function (s, k) {
+            return s + k / _this8.columns.size;
           }, 0);
         }).toList(), { index: this.index });
       }
@@ -770,13 +858,13 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'std',
     value: function std() {
-      var _this7 = this;
+      var _this9 = this;
 
       var axis = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
 
       if (axis === 0) {
         return new _series2.default(this.columns.toArray().map(function (k) {
-          return _this7.get(k).std();
+          return _this9.get(k).std();
         }), { index: this.columns.toArray() });
       } else if (axis === 1) {
         return this.variance(axis).map(function (v) {
@@ -820,28 +908,28 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'variance',
     value: function variance() {
-      var _this8 = this;
+      var _this10 = this;
 
       var axis = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
 
       if (axis === 0) {
         return new _series2.default(this.columns.toArray().map(function (k) {
-          return _this8.get(k).variance();
+          return _this10.get(k).variance();
         }), { index: this.columns.toArray() });
       } else if (axis === 1) {
-        var _ret2 = function () {
-          var means = _this8.mean(axis).values;
+        var _ret = function () {
+          var means = _this10.mean(axis).values;
           return {
-            v: new _series2.default(_immutable2.default.Range(0, _this8.length).map(function (idx) {
-              return _this8.values.get(idx).reduce(function (s, k) {
+            v: new _series2.default(_immutable2.default.Range(0, _this10.length).map(function (idx) {
+              return _this10.values.get(idx).reduce(function (s, k) {
                 var diff = k - means.get(idx);
-                return s + diff * diff / (_this8.columns.size - 1);
+                return s + diff * diff / (_this10.columns.size - 1);
               }, 0);
-            }).toArray(), { index: _this8.index })
+            }).toArray(), { index: _this10.index })
           };
         }();
 
-        if ((typeof _ret2 === 'undefined' ? 'undefined' : (0, _typeof3.default)(_ret2)) === "object") return _ret2.v;
+        if ((typeof _ret === 'undefined' ? 'undefined' : (0, _typeof3.default)(_ret)) === "object") return _ret.v;
       }
 
       throw new _exceptions.InvalidAxisError();
@@ -948,7 +1036,7 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'diff',
     value: function diff() {
-      var _this9 = this;
+      var _this11 = this;
 
       var periods = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 1;
       var axis = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 0;
@@ -958,13 +1046,13 @@ var DataFrame = function (_NDFrame) {
 
       if (axis === 0) {
         return new DataFrame(_immutable2.default.Map(this.columns.map(function (k) {
-          return [k, _this9._data.get(k).diff(periods)];
+          return [k, _this11._data.get(k).diff(periods)];
         })), { index: this.index });
       } else if (axis === 1) {
         return new DataFrame(_immutable2.default.Map(this.columns.map(function (k, idx) {
-          if (idx < periods) return [k, new _series2.default(_immutable2.default.Repeat(null, _this9.length).toList(), { name: k, index: _this9.index })];
-          var compareCol = _this9.get(_this9.columns.get(idx - periods));
-          return [k, _this9.get(k).map(function (v, vIdx) {
+          if (idx < periods) return [k, new _series2.default(_immutable2.default.Repeat(null, _this11.length).toList(), { name: k, index: _this11.index })];
+          var compareCol = _this11.get(_this11.columns.get(idx - periods));
+          return [k, _this11.get(k).map(function (v, vIdx) {
             return v - compareCol.iloc(vIdx);
           })];
         })), { index: this.index });
@@ -999,7 +1087,7 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'pct_change',
     value: function pct_change() {
-      var _this10 = this;
+      var _this12 = this;
 
       var periods = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 1;
       var axis = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 0;
@@ -1009,13 +1097,13 @@ var DataFrame = function (_NDFrame) {
 
       if (axis === 0) {
         return new DataFrame(_immutable2.default.Map(this.columns.map(function (k) {
-          return [k, _this10._data.get(k).pct_change(periods)];
+          return [k, _this12._data.get(k).pct_change(periods)];
         })), { index: this.index });
       } else if (axis === 1) {
         return new DataFrame(_immutable2.default.Map(this.columns.map(function (k, idx) {
-          if (idx < periods) return [k, new _series2.default(_immutable2.default.Repeat(null, _this10.length).toList(), { name: k, index: _this10.index })];
-          var compareCol = _this10.get(_this10.columns.get(idx - periods));
-          return [k, _this10.get(k).map(function (v, vIdx) {
+          if (idx < periods) return [k, new _series2.default(_immutable2.default.Repeat(null, _this12.length).toList(), { name: k, index: _this12.index })];
+          var compareCol = _this12.get(_this12.columns.get(idx - periods));
+          return [k, _this12.get(k).map(function (v, vIdx) {
             return v / compareCol.iloc(vIdx) - 1;
           })];
         })), { index: this.index });
@@ -1083,18 +1171,18 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'pivot',
     value: function pivot(index, columns, values) {
-      var _this11 = this;
+      var _this13 = this;
 
       var uniqueVals = _immutable2.default.Map({});
       var uniqueCols = _immutable2.default.List([]);
 
       this.index.forEach(function (v, idx) {
-        var idxVal = _this11.get(index).iloc(idx);
-        var colVal = _this11.get(columns).iloc(idx);
+        var idxVal = _this13.get(index).iloc(idx);
+        var colVal = _this13.get(columns).iloc(idx);
 
         if (uniqueVals.hasIn([idxVal, colVal])) throw new Error('pivot index and column must be unique');
 
-        var val = _this11.get(values).iloc(idx);
+        var val = _this13.get(values).iloc(idx);
 
         uniqueVals = uniqueVals.setIn([idxVal, colVal], val);
         if (!uniqueCols.has(colVal)) uniqueCols = uniqueCols.push(colVal);
@@ -1113,6 +1201,23 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'values',
     get: function get() {
+      var _this14 = this;
+
+      if (this._values instanceof _immutable2.default.List) return (0, _get3.default)(DataFrame.prototype.__proto__ || Object.getPrototypeOf(DataFrame.prototype), 'values', this);
+
+      var valuesList = _immutable2.default.List([]);
+
+      var _loop = function _loop(idx) {
+        valuesList = valuesList.concat([_immutable2.default.List(_this14.columns.map(function (k) {
+          return _this14._data.get(k).iloc(idx);
+        }))]);
+      };
+
+      for (var idx = 0; idx < this.length; idx += 1) {
+        _loop(idx);
+      }
+      this._values = valuesList;
+
       return (0, _get3.default)(DataFrame.prototype.__proto__ || Object.getPrototypeOf(DataFrame.prototype), 'values', this);
     }
 
@@ -1153,14 +1258,14 @@ var DataFrame = function (_NDFrame) {
      */
     ,
     set: function set(columns) {
-      var _this12 = this;
+      var _this15 = this;
 
       if (!Array.isArray(columns) || columns.length !== this.columns.size) throw new Error('Columns must be array of same dimension');
 
       var nextData = {};
       columns.forEach(function (k, idx) {
-        var prevColumn = _this12.columns.get(idx);
-        var prevSeries = _this12.get(prevColumn);
+        var prevColumn = _this15.columns.get(idx);
+        var prevSeries = _this15.get(prevColumn);
 
         prevSeries.name = k;
         nextData[k] = prevSeries;
@@ -1205,7 +1310,7 @@ var DataFrame = function (_NDFrame) {
      */
     ,
     set: function set(index) {
-      var _this13 = this;
+      var _this16 = this;
 
       this.set_axis(0, (0, _utils.parseIndex)(index, this._data.get(this.columns.get(0)).values));
 
@@ -1216,7 +1321,7 @@ var DataFrame = function (_NDFrame) {
             v = _ref10[1];
 
         // noinspection Eslint
-        v.index = _this13.index;
+        v.index = _this16.index;
       });
     }
 
@@ -1237,10 +1342,10 @@ var DataFrame = function (_NDFrame) {
   }, {
     key: 'length',
     get: function get() {
-      var _this14 = this;
+      var _this17 = this;
 
       return Math.max.apply(Math, (0, _toConsumableArray3.default)(this._data.keySeq().map(function (k) {
-        return _this14.get(k).length;
+        return _this17.get(k).length;
       }).toArray()));
     }
   }]);
diff --git a/src/js/core/series.js b/src/js/core/series.js
index 6f74b5e..20fd8e0 100644
--- a/src/js/core/series.js
+++ b/src/js/core/series.js
@@ -1285,6 +1285,61 @@ var Series = function (_NDFrame) {
 
       return new Series(valueIndexMap.values, { name: this.name, index: valueIndexMap.index });
     }
+
+    /**
+     * Convert the Series to a json object
+     *
+     * pandas equivalent: [Series.to_json](http://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.to_json.html)
+     *
+     * @param kwargs
+     * @param {string} [kwargs.orient=columns] orientation of JSON
+     *
+     * @returns {*}
+     *
+     * @example
+     * const ds = new Series([1, 2, 3], {name: 'x'});
+     *
+     * // Returns {0: 1, 1: 2, 2: 3}
+     * ds.to_json();
+     *
+     * // Returns [1, 2, 3]
+     * ds.to_json({orient: 'records'});
+     *
+     * // Returns {index: [0, 1, 2], name: 'x', values: [1, 2, 3]}
+     * ds.to_json({orient: 'split'});
+     */
+
+  }, {
+    key: 'to_json',
+    value: function to_json() {
+      var _this9 = this;
+
+      var kwargs = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : { orient: 'index' };
+
+      var ALLOWED_ORIENT = ['records', 'split', 'index'];
+      var orient = 'index';
+
+      if (typeof kwargs.orient !== 'undefined') {
+        if (ALLOWED_ORIENT.indexOf(kwargs.orient) < 0) throw new TypeError('orient must be in ' + ALLOWED_ORIENT);
+        orient = kwargs.orient;
+      }
+
+      var json = void 0;
+      switch (orient) {
+        case 'records':
+          return this.values.toArray();
+        case 'split':
+          return { index: this.index.toArray(), name: this.name, values: this.values.toJS() };
+        case 'index':
+          json = {};
+          this.values.forEach(function (v, idx) {
+            json[_this9.index.get(idx)] = v;
+          });
+          return json;
+        default:
+          throw new TypeError('orient must be in ' + ALLOWED_ORIENT);
+      }
+    }
   }, {
     key: 'kwargs',
     get: function get() {
diff --git a/src/js/core/structs.js b/src/js/core/structs.js
index d500c24..4612dc5 100644
--- a/src/js/core/structs.js
+++ b/src/js/core/structs.js
@@ -77,6 +77,7 @@ var Workbook = exports.Workbook = function () {
   }, {
     key: 'addSheet',
     value: function addSheet(sheetName, sheetContent) {
+      console.log(sheetContent.values);
       this._sheets.addSheet(sheetName, sheetContent);
     }
   }, {