Since at a given moment you have all the data you want to export on the screen (this as opposed to " I have pagination of data and each page is a different call to the server ") you can use the functions DOM native to iterate over the table, replacing the elements tr with line breaks and the td with commas. In pseudocode
- dado un string CSV=''
- genero un array vacío filas=[];
- dada una tabla
- por cada tr
- genero un array vacío columnas=[];
- por cada td
- agrego el contenido a "columnas"
- imploto "columnas" usando separador ","
- agrego el resultado a "filas"
- imploto "filas" usando separador salto de línea "\n"
- asigno el valor de lo anterior a CSV
All this to generate a great string, which will become the href attribute of a button, in the style:
var csv_href = 'data:application/csv;charset=utf-8,' + encodeURIComponent(CSV);
(here is a functional example in bl.ocks.org )
But what I would suggest is that you look for proven solutions for your use case, which is quite common. In my case, when I had to solve something similar years ago, I opted to use jQuery + DataTables with the extension buttons .
DataTables converts your static table into a more "dynamic" object that you can sort and filter (although that is not what you were looking for) and has extensions like the one that I tell you that allow you to download to different formats.
In the example below, I enabled the extension specifically for the Copy and Download to CSV buttons
$(document).ready(function() {
$('#example').DataTable( {
dom: 'Bfr',
buttons: [
{
extend: 'csv',
filename:'exportacion'
}
]
} );
} );
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdn.datatables.net/1.10.13/js/jquery.dataTables.min.js"></script>
<script src="https://cdn.datatables.net/buttons/1.2.4/js/dataTables.buttons.min.js
"></script>
<script src="https://cdn.datatables.net/buttons/1.2.4/js/buttons.html5.min.js"></script>
<link rel="stylesheet" href="https://cdn.datatables.net/1.10.13/css/jquery.dataTables.min.css">
<link rel="stylesheet" href="https://cdn.datatables.net/buttons/1.2.4/css/buttons.dataTables.min.css">
<table id="example" class="display nowrap" cellspacing="0" width="100%">
<thead>
<tr>
<th>Name</th>
<th>Position</th>
<th>Office</th>
<th>Age</th>
<th>Start date</th>
<th>Salary</th>
</tr>
</thead>
<tfoot>
<tr>
<th>Name</th>
<th>Position</th>
<th>Office</th>
<th>Age</th>
<th>Start date</th>
<th>Salary</th>
</tr>
</tfoot>
<tbody>
<tr>
<td>Tiger Nixon</td>
<td>System Architect</td>
<td>Edinburgh</td>
<td>61</td>
<td>2011/04/25</td>
<td>$320,800</td>
</tr>
<tr>
<td>Garrett Winters</td>
<td>Accountant</td>
<td>Tokyo</td>
<td>63</td>
<td>2011/07/25</td>
<td>$170,750</td>
</tr>
<tr>
<td>Ashton Cox</td>
<td>Junior Technical Author</td>
<td>San Francisco</td>
<td>66</td>
<td>2009/01/12</td>
<td>$86,000</td>
</tr>
<tr>
<td>Cedric Kelly</td>
<td>Senior Javascript Developer</td>
<td>Edinburgh</td>
<td>22</td>
<td>2012/03/29</td>
<td>$433,060</td>
</tr>
<tr>
<td>Airi Satou</td>
<td>Accountant</td>
<td>Tokyo</td>
<td>33</td>
<td>2008/11/28</td>
<td>$162,700</td>
</tr>
<tr>
<td>Brielle Williamson</td>
<td>Integration Specialist</td>
<td>New York</td>
<td>61</td>
<td>2012/12/02</td>
<td>$372,000</td>
</tr>
<tr>
<td>Herrod Chandler</td>
<td>Sales Assistant</td>
<td>San Francisco</td>
<td>59</td>
<td>2012/08/06</td>
<td>$137,500</td>
</tr>
<tr>
<td>Rhona Davidson</td>
<td>Integration Specialist</td>
<td>Tokyo</td>
<td>55</td>
<td>2010/10/14</td>
<td>$327,900</td>
</tr>
<tr>
<td>Colleen Hurst</td>
<td>Javascript Developer</td>
<td>San Francisco</td>
<td>39</td>
<td>2009/09/15</td>
<td>$205,500</td>
</tr>
<tr>
<td>Sonya Frost</td>
<td>Software Engineer</td>
<td>Edinburgh</td>
<td>23</td>
<td>2008/12/13</td>
<td>$103,600</td>
</tr>
<tr>
<td>Jena Gaines</td>
<td>Office Manager</td>
<td>London</td>
<td>30</td>
<td>2008/12/19</td>
<td>$90,560</td>
</tr>
<tr>
<td>Quinn Flynn</td>
<td>Support Lead</td>
<td>Edinburgh</td>
<td>22</td>
<td>2013/03/03</td>
<td>$342,000</td>
</tr>
<tr>
<td>Charde Marshall</td>
<td>Regional Director</td>
<td>San Francisco</td>
<td>36</td>
<td>2008/10/16</td>
<td>$470,600</td>
</tr>
<tr>
<td>Haley Kennedy</td>
<td>Senior Marketing Designer</td>
<td>London</td>
<td>43</td>
<td>2012/12/18</td>
<td>$313,500</td>
</tr>
<tr>
<td>Tatyana Fitzpatrick</td>
<td>Regional Director</td>
<td>London</td>
<td>19</td>
<td>2010/03/17</td>
<td>$385,750</td>
</tr>
<tr>
<td>Michael Silva</td>
<td>Marketing Designer</td>
<td>London</td>
<td>66</td>
<td>2012/11/27</td>
<td>$198,500</td>
</tr>
<tr>
<td>Paul Byrd</td>
<td>Chief Financial Officer (CFO)</td>
<td>New York</td>
<td>64</td>
<td>2010/06/09</td>
<td>$725,000</td>
</tr>
<tr>
<td>Gloria Little</td>
<td>Systems Administrator</td>
<td>New York</td>
<td>59</td>
<td>2009/04/10</td>
<td>$237,500</td>
</tr>
<tr>
<td>Bradley Greer</td>
<td>Software Engineer</td>
<td>London</td>
<td>41</td>
<td>2012/10/13</td>
<td>$132,000</td>
</tr>
<tr>
<td>Dai Rios</td>
<td>Personnel Lead</td>
<td>Edinburgh</td>
<td>35</td>
<td>2012/09/26</td>
<td>$217,500</td>
</tr>
<tr>
<td>Jenette Caldwell</td>
<td>Development Lead</td>
<td>New York</td>
<td>30</td>
<td>2011/09/03</td>
<td>$345,000</td>
</tr>
<tr>
<td>Yuri Berry</td>
<td>Chief Marketing Officer (CMO)</td>
<td>New York</td>
<td>40</td>
<td>2009/06/25</td>
<td>$675,000</td>
</tr>
<tr>
<td>Caesar Vance</td>
<td>Pre-Sales Support</td>
<td>New York</td>
<td>21</td>
<td>2011/12/12</td>
<td>$106,450</td>
</tr>
<tr>
<td>Doris Wilder</td>
<td>Sales Assistant</td>
<td>Sidney</td>
<td>23</td>
<td>2010/09/20</td>
<td>$85,600</td>
</tr>
<tr>
<td>Angelica Ramos</td>
<td>Chief Executive Officer (CEO)</td>
<td>London</td>
<td>47</td>
<td>2009/10/09</td>
<td>$1,200,000</td>
</tr>
<tr>
<td>Gavin Joyce</td>
<td>Developer</td>
<td>Edinburgh</td>
<td>42</td>
<td>2010/12/22</td>
<td>$92,575</td>
</tr>
<tr>
<td>Jennifer Chang</td>
<td>Regional Director</td>
<td>Singapore</td>
<td>28</td>
<td>2010/11/14</td>
<td>$357,650</td>
</tr>
<tr>
<td>Brenden Wagner</td>
<td>Software Engineer</td>
<td>San Francisco</td>
<td>28</td>
<td>2011/06/07</td>
<td>$206,850</td>
</tr>
<tr>
<td>Fiona Green</td>
<td>Chief Operating Officer (COO)</td>
<td>San Francisco</td>
<td>48</td>
<td>2010/03/11</td>
<td>$850,000</td>
</tr>
<tr>
<td>Shou Itou</td>
<td>Regional Marketing</td>
<td>Tokyo</td>
<td>20</td>
<td>2011/08/14</td>
<td>$163,000</td>
</tr>
<tr>
<td>Michelle House</td>
<td>Integration Specialist</td>
<td>Sidney</td>
<td>37</td>
<td>2011/06/02</td>
<td>$95,400</td>
</tr>
<tr>
<td>Suki Burks</td>
<td>Developer</td>
<td>London</td>
<td>53</td>
<td>2009/10/22</td>
<td>$114,500</td>
</tr>
<tr>
<td>Prescott Bartlett</td>
<td>Technical Author</td>
<td>London</td>
<td>27</td>
<td>2011/05/07</td>
<td>$145,000</td>
</tr>
<tr>
<td>Gavin Cortez</td>
<td>Team Leader</td>
<td>San Francisco</td>
<td>22</td>
<td>2008/10/26</td>
<td>$235,500</td>
</tr>
<tr>
<td>Martena Mccray</td>
<td>Post-Sales support</td>
<td>Edinburgh</td>
<td>46</td>
<td>2011/03/09</td>
<td>$324,050</td>
</tr>
<tr>
<td>Unity Butler</td>
<td>Marketing Designer</td>
<td>San Francisco</td>
<td>47</td>
<td>2009/12/09</td>
<td>$85,675</td>
</tr>
<tr>
<td>Howard Hatfield</td>
<td>Office Manager</td>
<td>San Francisco</td>
<td>51</td>
<td>2008/12/16</td>
<td>$164,500</td>
</tr>
<tr>
<td>Hope Fuentes</td>
<td>Secretary</td>
<td>San Francisco</td>
<td>41</td>
<td>2010/02/12</td>
<td>$109,850</td>
</tr>
<tr>
<td>Vivian Harrell</td>
<td>Financial Controller</td>
<td>San Francisco</td>
<td>62</td>
<td>2009/02/14</td>
<td>$452,500</td>
</tr>
<tr>
<td>Timothy Mooney</td>
<td>Office Manager</td>
<td>London</td>
<td>37</td>
<td>2008/12/11</td>
<td>$136,200</td>
</tr>
<tr>
<td>Jackson Bradshaw</td>
<td>Director</td>
<td>New York</td>
<td>65</td>
<td>2008/09/26</td>
<td>$645,750</td>
</tr>
<tr>
<td>Olivia Liang</td>
<td>Support Engineer</td>
<td>Singapore</td>
<td>64</td>
<td>2011/02/03</td>
<td>$234,500</td>
</tr>
<tr>
<td>Bruno Nash</td>
<td>Software Engineer</td>
<td>London</td>
<td>38</td>
<td>2011/05/03</td>
<td>$163,500</td>
</tr>
<tr>
<td>Sakura Yamamoto</td>
<td>Support Engineer</td>
<td>Tokyo</td>
<td>37</td>
<td>2009/08/19</td>
<td>$139,575</td>
</tr>
<tr>
<td>Thor Walton</td>
<td>Developer</td>
<td>New York</td>
<td>61</td>
<td>2013/08/11</td>
<td>$98,540</td>
</tr>
<tr>
<td>Finn Camacho</td>
<td>Support Engineer</td>
<td>San Francisco</td>
<td>47</td>
<td>2009/07/07</td>
<td>$87,500</td>
</tr>
<tr>
<td>Serge Baldwin</td>
<td>Data Coordinator</td>
<td>Singapore</td>
<td>64</td>
<td>2012/04/09</td>
<td>$138,575</td>
</tr>
<tr>
<td>Zenaida Frank</td>
<td>Software Engineer</td>
<td>New York</td>
<td>63</td>
<td>2010/01/04</td>
<td>$125,250</td>
</tr>
<tr>
<td>Zorita Serrano</td>
<td>Software Engineer</td>
<td>San Francisco</td>
<td>56</td>
<td>2012/06/01</td>
<td>$115,000</td>
</tr>
<tr>
<td>Jennifer Acosta</td>
<td>Junior Javascript Developer</td>
<td>Edinburgh</td>
<td>43</td>
<td>2013/02/01</td>
<td>$75,650</td>
</tr>
<tr>
<td>Cara Stevens</td>
<td>Sales Assistant</td>
<td>New York</td>
<td>46</td>
<td>2011/12/06</td>
<td>$145,600</td>
</tr>
<tr>
<td>Hermione Butler</td>
<td>Regional Director</td>
<td>London</td>
<td>47</td>
<td>2011/03/21</td>
<td>$356,250</td>
</tr>
<tr>
<td>Lael Greer</td>
<td>Systems Administrator</td>
<td>London</td>
<td>21</td>
<td>2009/02/27</td>
<td>$103,500</td>
</tr>
<tr>
<td>Jonas Alexander</td>
<td>Developer</td>
<td>San Francisco</td>
<td>30</td>
<td>2010/07/14</td>
<td>$86,500</td>
</tr>
<tr>
<td>Shad Decker</td>
<td>Regional Director</td>
<td>Edinburgh</td>
<td>51</td>
<td>2008/11/13</td>
<td>$183,000</td>
</tr>
<tr>
<td>Michael Bruce</td>
<td>Javascript Developer</td>
<td>Singapore</td>
<td>29</td>
<td>2011/06/27</td>
<td>$183,000</td>
</tr>
<tr>
<td>Donna Snider</td>
<td>Customer Support</td>
<td>New York</td>
<td>27</td>
<td>2011/01/25</td>
<td>$112,000</td>
</tr>
</tbody>
</table>
Probably my answer goes beyond the scope of this question but, again, if the wheel is already invented, it does not make sense to reinvent it.
Edit : I added a configuration to give the file an appropriate name. Thank you Mauricio Arias Olave for the suggestion.
Edit2 : The example is a simplification of the full example that appears in the documentation of the buttons extension, removing the parts that are not needed to export CSV.