# DataTables example Footer callback

Through the use of the header and footer callback manipulation functions provided by DataTables (`headerCallbackDT` and `footerCallbackDT`), it is possible to perform some powerful and useful data manipulation functions, such as summarising data in the table.

The example below shows a footer callback being used to total the data for a column (both the visible and the hidden data) using the `column().data()DT` API method and `column().footer()DT` for writing the value into the footer.

First name | Last name | Position | Office | Salary
--- | --- | --- | --- | ---
Total: |
Tiger | Nixon | System Architect | Edinburgh | $320,800
Garrett | Winters | Accountant | Tokyo | $170,750
Ashton | Cox | Junior Technical Author | San Francisco | $86,000
Cedric | Kelly | Senior Javascript Developer | Edinburgh | $433,060
Airi | Satou | Accountant | Tokyo | $162,700
Brielle | Williamson | Integration Specialist | New York | $372,000
Herrod | Chandler | Sales Assistant | San Francisco | $137,500
Rhona | Davidson | Integration Specialist | Tokyo | $327,900
Colleen | Hurst | Javascript Developer | San Francisco | $205,500
Sonya | Frost | Software Engineer | Edinburgh | $103,600
Jena | Gaines | Office Manager | London | $90,560
Quinn | Flynn | Support Lead | Edinburgh | $342,000
Charde | Marshall | Regional Director | San Francisco | $470,600
Haley | Kennedy | Senior Marketing Designer | London | $313,500
Tatyana | Fitzpatrick | Regional Director | London | $385,750
Michael | Silva | Marketing Designer | London | $198,500
Paul | Byrd | Chief Financial Officer (CFO) | New York | $725,000
Gloria | Little | Systems Administrator | New York | $237,500
Bradley | Greer | Software Engineer | London | $132,000
Dai | Rios | Personnel Lead | Edinburgh | $217,500
Jenette | Caldwell | Development Lead | New York | $345,000
Yuri | Berry | Chief Marketing Officer (CMO) | New York | $675,000
Caesar | Vance | Pre-Sales Support | New York | $106,450
Doris | Wilder | Sales Assistant | Sidney | $85,600
Angelica | Ramos | Chief Executive Officer (CEO) | London | $1,200,000
Gavin | Joyce | Developer | Edinburgh | $92,575
Jennifer | Chang | Regional Director | Singapore | $357,650
Brenden | Wagner | Software Engineer | San Francisco | $206,850
Fiona | Green | Chief Operating Officer (COO) | San Francisco | $850,000
Shou | Itou | Regional Marketing | Tokyo | $163,000
Michelle | House | Integration Specialist | Sidney | $95,400
Suki | Burks | Developer | London | $114,500
Prescott | Bartlett | Technical Author | London | $145,000
Gavin | Cortez | Team Leader | San Francisco | $235,500
Martena | Mccray | Post-Sales support | Edinburgh | $324,050
Unity | Butler | Marketing Designer | San Francisco | $85,675
Howard | Hatfield | Office Manager | San Francisco | $164,500
Hope | Fuentes | Secretary | San Francisco | $109,850
Vivian | Harrell | Financial Controller | San Francisco | $452,500
Timothy | Mooney | Office Manager | London | $136,200
Jackson | Bradshaw | Director | New York | $645,750
Olivia | Liang | Support Engineer | Singapore | $234,500
Bruno | Nash | Software Engineer | London | $163,500
Sakura | Yamamoto | Support Engineer | Tokyo | $139,575
Thor | Walton | Developer | New York | $98,540
Finn | Camacho | Support Engineer | San Francisco | $87,500
Serge | Baldwin | Data Coordinator | Singapore | $138,575
Zenaida | Frank | Software Engineer | New York | $125,250
Zorita | Serrano | Software Engineer | San Francisco | $115,000
Jennifer | Acosta | Junior Javascript Developer | Edinburgh | $75,650
Cara | Stevens | Sales Assistant | New York | $145,600
Hermione | Butler | Regional Director | London | $356,250
Lael | Greer | Systems Administrator | London | $103,500
Jonas | Alexander | Developer | San Francisco | $86,500
Shad | Decker | Regional Director | Edinburgh | $183,000
Michael | Bruce | Javascript Developer | Singapore | $183,000
Donna | Snider | Customer Support | New York | $112,000

- Javascript
- HTML
- CSS
- Ajax
- Server-side script

The Javascript shown below is used to initialise the table shown in this example:

`$(document).ready(function() { $('#example').dataTable( { "footerCallback": function ( row, data, start, end, display ) { var api = this.api(), data; // Remove the formatting to get integer data for summation var intVal = function ( i ) { return typeof i === 'string' ? i.replace(/[\$,]/g, '')*1 : typeof i === 'number' ? i : 0; }; // Total over all pages total = api .column( 4 ) .data() .reduce( function (a, b) { return intVal(a) + intVal(b); } ); // Total over this page pageTotal = api .column( 4, { page: 'current'} ) .data() .reduce( function (a, b) { return intVal(a) + intVal(b); }, 0 ); // Update footer $( api.column( 4 ).footer() ).html( '$'+pageTotal +' ( $'+ total +' total)' ); } } ); } );`

In addition to the above code, the following Javascript library files are loaded for use in this example:

- ../../media/js/jquery.js
- ../../media/js/jquery.dataTables.js

The HTML shown below is the raw HTML table element, before it has been enhanced by DataTables:

This example uses a little bit of additional CSS beyond what is loaded from the library files (below), in order to correctly display the table. The additional CSS used is shown below:

`th { white-space: nowrap; }`

The following CSS library files are loaded for use in this example to provide the styling of the table:

- ../../media/css/jquery.dataTables.css

This table loads data by Ajax. The latest data that has been loaded is shown below. This data will update automatically as any additional data is loaded.

The script used to perform the server-side processing for this table is shown below. Please note that this is just an example script using PHP. Server-side processing scripts can be written in any language, using the protocol described in the DataTables documentation.