How to export all rows from DataTables using server side (ajax)

According to DataTables documentation there is no way to export all rows when you are using server side:

Special note on server-side processing: When using DataTables in server-side processing mode (serverSide) the selector-modifier has very little effect on the rows selected since all processing (ordering, search etc) is performed at the server. Therefore, the only rows that exist on the client-side are those shown in the table at any one time, and the selector can only select those rows which are on the current page.

However, it is possible to actually override some DataTable internal method to make this happen, without modifying its source code. More specifically, you override the method responsible for extracting the current’s page lines to actually pull the  data from your server side.

You have to add the code for overriding the export just before initializing your dataTable. The final code would look like this:

$(document).ready(function() {

    jQuery.fn.DataTable.Api.register( 'buttons.exportData()', function ( options ) {
            if ( this.context.length ) {
                var jsonResult = $.ajax({
                    url: 'myServerSide.json?page=all',
                    data: {search: $("#search").val()},
                    success: function (result) {
                        //Do nothing
                    },
                    async: false
                });

                return {body: jsonResult.responseJSON.data, header: $("#myTable thead tr th").map(function() { return this.innerHTML; }).get()};
            }
        } );

    $("#myTable ").DataTable(
        {
            "dom": 'lBrtip',
            "pageLength": 5, 
            "buttons": ['csv','print', 'excel', 'pdf'],
            "processing": true,
            "serverSide": true,
            "ajax": {
                "url": "myServerSide.json",
                "type": 'GET',
                "data": {search: $("#search").val()} 
            }
        }
});

Let’s remember there are two ways to handle Ajx json data on DataTables. The first and easier to make the export happen, is to use arrays. If you’re using objects, you have to parse them into arrays, because the buttons.exportData() function is supposed to return the data in array. (Like this ->  [[1, “John”], [2, “Jen”], [3, “Ross”]])