Array of columns with a single variable + defaultColumns in Datatables

I’m trying to create dynamic columns in my Datatables.

Suppose I want to create 4 columns + default column (2 buttons). Well, we would do the following (this works):

$('#tablaUsuarios').DataTable({
     "columns": [
          {"data": "usuario"},
          {"data": "apellido1"},
          {"data": "apellido2"},
          {"data": "email"},
          {"defaultContent": "<div class='text-center'><div class='btn-group'><button class='btn btn-primary btn-sm btnEditar' value='edit'><i class='material-icons'>edit</i></button><button class='btn btn-danger btn-sm btnBorrar'><i class='material-icons' value='delete'>delete</i></button></div></div>"}
      ],
});

Now suppose I want to do the SAME thing, but with a single value, something like this:

var dataHeader = <?=$fields?>;

$('#tablaUsuarios').DataTable({
     "columns": [
          dataHeader,
          "defaultContent": "<div class='text-center'><div class='btn-group'><button class='btn btn-primary btn-sm btnEditar' value='edit'><i class='material-icons'>edit</i></button><button class='btn btn-danger btn-sm btnBorrar'><i class='material-icons' value='delete'>delete</i></button></div></div>"
      ],
});

dataHeader contains the following:

0: {data: "id", mData: "id"}
1: {data: "usuario", mData: "usuario"}
2: {data: "apellido1", mData: "apellido1"}
3: {data: "apellido2", mData: "apellido2"}
4: {data: "email", mData: "email"}
length: 5
__proto__: Array(0)

(Is a copy paste from console.log from my browser because I need reputation to upload images).

As all of you can see, it has the same format but it doesn’t show the defaultColumns and I don’t know why. I don’t get any type of error.

Does anyone know if it is possible to do something like this?

This is my full code:

<?php

include_once(DIR_PLUGINS.'/alexcrudgenerator/main.php');

    $test = new GenerateCrud($_POST['tableName'], $_POST['id'], $_POST['tableFields']);

    switch($_POST['action']){
        
        case 'datosTabla':
            
            $res = json_decode($_POST['datos']);
            echo json_encode($res, JSON_UNESCAPED_UNICODE);
            
            break;

        case 'showtable':

            $res = getEntireTable($_POST['tableName'], $_POST['id'], $_POST['tableFields']);
            
            foreach ($res as $data){
                $resultados['data'][] = $data;
            }           
            $resultados = json_encode($resultados);
            
            foreach(json_decode($_POST['tableFields']) as $columnsDB){
                $fields[] = array('data'=>$columnsDB);;
            }
            $fields = json_encode($fields);
?>
            <div class="container caja">
                <div class="row">
                    <div class="col-lg-12 col-sm-12">
                        <div>
                            <table id="tablaUsuarios" class="table table-striped table-bordered table-condensed" style="width:100%" >
                                <thead class="text-center">
                                </thead>
                                <tbody>
                                </tbody>
                            </table>
                        </div>
                  </div>
            </div>

            <script>
            
                $(document).ready(function() {
                    var datos = '<?=$resultados?>';
                    var dataHeader = <?=$fields?>;
                    

                    console.log(dataHeader);
                    
                    $('#tablaUsuarios').DataTable({
                        "language": {"url": "//cdn.datatables.net/plug-ins/1.10.20/i18n/Spanish.json"},
                        "paging": true,
                        "lengthChange": true,
                        "searching": true,
                        "info": true,
                        "autoWidth": true,
                        "scrollX": true,

                        "ajax":{            
                            "url": '<?=SITE_URL_ADMIN?>/alexcrudgenerator/crud/res/',
                            "method": 'POST',
                            "data":{action: "datosTabla", datos: datos}
                        },

                        "columns":
                            dataHeader,
                            "defaultContent": "<div class='text-center'><div class='btn-group'><button class='btn btn-primary btn-sm btnEditar' value='edit'><i class='material-icons'>edit</i></button><button class='btn btn-danger btn-sm btnBorrar'><i class='material-icons' value='delete'>delete</i></button></div></div>",
                        
                        success: function() {
                            alert("Hello, successful!");
                        }
                    });
                })
            </script>
<?php
        break;      
}
?>

Also, as an additional question, how can I add values in my TH? I mean, add like a title for each column.

Also, as an additional question, how can I add values in my TH? I mean, add like a title for each column.

I tryied to add <tr><td>Test 1</td></tr> in my <thead></thead>, but nothing …

Thank you in advance, guys.

Answer

The problem is happening because the dataHeader variable is an array, so what it actually looks like is this:

var dataHeader = [
  { "data": "id" },
  { "data": "usuario" },
  { "data": "apellido1" },
  { "data": "apellido2" },
  { "data": "email" }
];

---

Side Note: I simplified your variable because it appears to contain both data and mData options:

{ data: "id", mData: "id" }, ...

Whereas it only needs to contain data options:

{ data: "id" }, ...

mData is the old name for data – so these options are equivalent.

---

If you take this array and add it into your DataTable, you end up with the following structure for the columns option:

"columns": [
  [
    { "data": "id" },
    { "data": "usuario" },
    { "data": "apellido1" },
    { "data": "apellido2" },
    { "data": "email" }
  ],
  "defaultContent": "<div class='text-center'>...</div>"
],

And this is not what you want – you have that extra array inside the columns array. This is not valid for DataTables.

Solution:

You can work around this by taking that HTML string and adding it to the array provided by PHP:

var defaultContent = { defaultContent: "<div class='text-center'>...</div>" }

var dynamicColumns= <?=$fields?>;

dynamicColumns.push(defaultContent);

The push() function adds the defaultContent object to the end of the dynamicColumns array.

Now you can use this new variable dynamicColumns in your DataTable:

$('#tablaUsuarios').DataTable({
  "columns": dynamicColumns
});