to_excel writer with option to download in browser

package.json

@@ -18,7 +18,9 @@
   ],
   "dependencies": {
     "babel-plugin-transform-runtime": "^6.15.0",
-    "immutable": "^3.8.1"
+    "file-saver": "^1.3.3",
+    "immutable": "^3.8.1",
+    "xlsx": "^0.8.1"
   },
   "devDependencies": {
     "babel-cli": "^6.18.0",

src/es6/__tests__/core/frame.js

@@ -2,6 +2,7 @@ import Immutable from 'immutable';
 
 import DataFrame, {mergeDataFrame} from '../../core/frame';
 import Series from '../../core/series';
+import { Workbook } from '../../core/structs';
 import {IndexMismatchError} from '../../core/exceptions';
 
 
@@ -330,6 +331,20 @@ describe('frame', () => {
     });
   });
 
+  describe('to_excel', () => {
+    it('converts a pandas DataFrame to a properly formatted Excel file', () => {
+      const df = new DataFrame(Immutable.Map({x: new Series([1, 2, 3]), y: new Series([2, 3, 4])}));
+
+      const originalURL = window.URL;
+      window.URL = {
+        createObjectURL: (blob) => { console.log(blob); return "something"; },
+      };
+      console.log(df.to_excel(new Workbook(), 'my test sheet', true));
+
+      window.URL = originalURL;
+    });
+  });
+
   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}]);

src/es6/core/frame.js

@@ -1,9 +1,11 @@
 
 import Immutable from 'immutable';
+import { saveAs } from 'file-saver';
 
 import { InvalidAxisError } from './exceptions';
 import NDFrame from './generic';
 import Series from './series';
+import { Workbook, Sheet } from './structs';
 import { enumerate, nonMergeColumns, intersectingColumns, parseIndex } from './utils';
 
 
@@ -562,6 +564,49 @@ export default class DataFrame extends NDFrame {
     return csvString;
   }
 
+  /**
+   * Write the `DataFrame` to a Workbook object
+   *
+   * @param {string|Workbook} excel_writer
+   *    File path or existing Workbook object
+   * @param {string} sheetName
+   *    Name of sheet which will contain DataFrame
+   * @param {boolean} download
+   *    Download the excel file?
+   *
+   * @return {Workbook}
+   *
+   * @example
+   *
+   */
+  to_excel(excel_writer, sheetName = 'Sheet1', download = false) {
+    let wb;
+    if (excel_writer instanceof Workbook) {
+      const sheet = new Sheet(this.values);
+
+      wb = excel_writer.copy();
+      wb.addSheet(sheetName, sheet);
+    } else if (typeof excel_writer === 'string') {
+      wb = new Workbook();
+      wb.addSheet(sheetName, new Sheet(this.values));
+    } 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;
+      return buf;
+    }
+
+    if (download) {
+      saveAs(new Blob([s2ab(wb.writeWorkbook())],
+        {type: "application/octet-stream"}),
+        typeof excel_writer === 'string' ? excel_writer : 'StratoDem Download.xlsx');
+    }
+
+    return wb;
+  }
+
   /**
    * Return the sum of the values in the `DataFrame` along the axis
    *

src/es6/core/structs.js

@@ -0,0 +1,160 @@
+/**
+ * structs
+ *
+ * Description:
+ * Primary author(s):
+ * Secondary author(s):
+ *
+ * Notes:
+ *
+ * January 12, 2017
+ * StratoDem Analytics, LLC
+ */
+
+import Immutable from 'immutable';
+import XLSX from 'xlsx';
+
+// This does not match the Python pandas
+
+export class Workbook {
+  /**
+   * @param {Sheets} sheets
+   */
+  constructor(sheets = new Sheets({})) {
+    this._sheets = sheets;
+  }
+
+  /**
+   * @returns {Sheets}
+   */
+  get sheets() {
+    return this._sheets;
+  }
+
+  get SheetNames() {
+    return this.sheets.sheetNames.toArray();
+  }
+
+  get Sheets() {
+    return this.sheets.sheets.toJS();
+  }
+
+  /**
+   * Create a copy of the Workbook
+   *
+   * @returns {Workbook}
+   */
+  copy() {
+    return new Workbook(this._sheets);
+  }
+
+  /**
+   * Add a sheet to the Workbook
+   *
+   * @param {string} sheetName
+   * @param {Sheet} sheetContent
+   */
+  addSheet(sheetName, sheetContent) {
+    this._sheets.addSheet(sheetName, sheetContent);
+  }
+
+  writeWorkbook() {
+    return XLSX.write(this, {bookType: 'xlsx', bookSST: true, type: 'binary'});
+  }
+}
+
+
+class Sheets {
+  constructor(initialSheets = {}) {
+    this._sheets = Immutable.Map(initialSheets);
+    this._sheetNames = this._sheets.keySeq().toList();
+  }
+
+  /**
+   * List of sheet names in the Sheets
+   *
+   * @returns {List<number|string>}
+   */
+  get sheetNames() {
+    return this._sheetNames;
+  }
+
+  /**
+   * Map of sheetName, Sheet objects
+   *
+   * @returns {Map<string, Sheet>}
+   */
+  get sheets() {
+    return this._sheets;
+  }
+
+  /**
+   *
+   * @param {string} sheetName
+   * @param {Sheet} sheetContent
+   */
+  addSheet(sheetName, sheetContent) {
+    this._sheets = this._sheets.set(sheetName, sheetContent);
+  }
+}
+
+
+export class Sheet {
+  /**
+   * Construct a Sheet object from a List of Lists of data (from DataFrame.values, e.g.)
+   *
+   * @param {List<List>} data
+   */
+  constructor(data) {
+    this._sheet = this._sheet_from_list_of_lists(data);
+  }
+
+  get sheet() {
+    return this._sheet;
+  }
+
+  /**
+   * Get a Sheet object's content from a List of Lists
+   * As inspiration: view-source:http://sheetjs.com/demos/writexlsx.html
+   *
+   * @param data
+   * @private
+   */
+  _sheet_from_list_of_lists(data) {
+    const range = {s: {c: 10000000, r: 10000000}, e: {c: 0, r: 0}};
+    const ws = {};
+
+    function datenum(v, date1904) {
+      const epoch = Date.parse(date1904 ? v + 1462 : v);
+      return (epoch - new Date(Date.UTC(1899, 11, 30))) / (24 * 60 * 60 * 1000);
+    }
+
+    data.forEach((row, idxRow) => {
+      row.forEach((v, idxCol) => {
+        if (v === null) return;
+
+        if (range.s.r > idxRow) range.s.r = idxRow;
+        if (range.s.c > idxCol) range.s.c = idxCol;
+        if (range.e.r < idxRow) range.e.r = idxRow;
+        if (range.e.c < idxCol) range.e.c = idxCol;
+
+        const cell = {v};
+        const cell_ref = XLSX.utils.encode_cell({c: idxCol, r: idxRow});
+
+        if (typeof cell.v === 'number')
+          cell.t = 'n';
+        else if (cell.v instanceof Date) {
+          cell.t = 'n'; cell.z = XLSX.SSF._table[14];
+          cell.v = datenum(cell.v);
+        } else
+          cell.t = 's';
+
+        ws[cell_ref] = cell;
+      });
+    });
+
+    if (range.s.c < 10000000) ws['!ref'] = XLSX.utils.encode_range(range);
+
+    return ws;
+  }
+}

src/es6/io/parsers.js

@@ -10,4 +10,4 @@
  */
 export const read_csv = (filepath, callback, args) => {
   throw new Error('Not implemented');
-};
+};

src/js/__tests__/core/frame.js

@@ -16,6 +16,8 @@ var _series = require('../../core/series');
 
 var _series2 = _interopRequireDefault(_series);
 
+var _structs = require('../../core/structs');
+
 var _exceptions = require('../../core/exceptions');
 
 function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
@@ -372,6 +374,22 @@ describe('frame', function () {
     });
   });
 
+  describe('to_excel', function () {
+    it('converts a pandas DataFrame to a properly formatted Excel file', function () {
+      var df = new _frame2.default(_immutable2.default.Map({ x: new _series2.default([1, 2, 3]), y: new _series2.default([2, 3, 4]) }));
+
+      var originalURL = window.URL;
+      window.URL = {
+        createObjectURL: function createObjectURL(blob) {
+          console.log(blob);return "something";
+        }
+      };
+      console.log(df.to_excel(new _structs.Workbook(), 'my test sheet', true));
+
+      window.URL = originalURL;
+    });
+  });
+
   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 }]);

src/js/core/frame.js

@@ -41,6 +41,8 @@ var _immutable = require('immutable');
 
 var _immutable2 = _interopRequireDefault(_immutable);
 
+var _fileSaver = require('file-saver');
+
 var _exceptions = require('./exceptions');
 
 var _generic = require('./generic');
@@ -51,6 +53,8 @@ var _series = require('./series');
 
 var _series2 = _interopRequireDefault(_series);
 
+var _structs = require('./structs');
+
 var _utils = require('./utils');
 
 function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
@@ -581,6 +585,54 @@ var DataFrame = function (_NDFrame) {
       return csvString;
     }
 
+    /**
+     * Write the `DataFrame` to a Workbook object
+     *
+     * @param {string|Workbook} excel_writer
+     *    File path or existing Workbook object
+     * @param {string} sheetName
+     *    Name of sheet which will contain DataFrame
+     * @param {boolean} download
+     *    Download the excel file?
+     *
+     * @return {Workbook}
+     *
+     * @example
+     *
+     */
+
+  }, {
+    key: 'to_excel',
+    value: function to_excel(excel_writer) {
+      var sheetName = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 'Sheet1';
+      var download = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : false;
+
+      var wb = void 0;
+      if (excel_writer instanceof _structs.Workbook) {
+        var sheet = new _structs.Sheet(this.values);
+
+        wb = excel_writer.copy();
+        wb.addSheet(sheetName, sheet);
+      } else if (typeof excel_writer === 'string') {
+        wb = new _structs.Workbook();
+        wb.addSheet(sheetName, new _structs.Sheet(this.values));
+      } 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) {
+          view[i] = s.charCodeAt(i) && 0xFF;
+        }return buf;
+      }
+
+      if (download) {
+        (0, _fileSaver.saveAs)(new Blob([s2ab(wb.writeWorkbook())], { type: "application/octet-stream" }), typeof excel_writer === 'string' ? excel_writer : 'StratoDem Download.xlsx');
+      }
+
+      return wb;
+    }
+
     /**
      * Return the sum of the values in the `DataFrame` along the axis
      *