Yii2: Get selected rows data from gridView checkbox columns into controller

I've view page(index.php) in my Yii2 project, and I'm using Kartik gridView for showing the data

This the view from index.php:

On the right side of view, I've a checkbox column. And I've an Export button. I want to export the selected name (selected by checkbox) into name.txt file.

I've finally make the export function, but I don't know how to get the selected data from view into controller.

I've try suggestions that I got from many forums, for example:

I put this javascript code in my view index.php:

<script>
function getRows(){
    var keys = $('#grid').yiiGridView('getSelectedRows');
    $.post({
        url: FakturOutController / exportAction,
        dataType: 'json',
        data: {keylist: keys},
        success: function(data) {
            alert('I did it! Processed checked rows.')
        },
    });
}

and set the export button like this:

<p>
    <button type="button" onclick="displayResult()" class="btn btn-success">Export</button>
</p>

But I got nothing, the button didn't showed any action/reaction when clicked.

Any help would be appreciated. Thanks