Simple Laravel Backpack text filter for a single field

CrudController.php

<?php /** app/Http/Controllers/CrudController.php **/

namespace App\Http\Controllers;

use Illuminate\Http\Response;

class CrudController extends \Backpack\CRUD\app\Http\Controllers\CrudController
{
    public function setUp()
    {
      // ...
      $this->crud->addFilter(
            [
                'type' => 'text',
                'name' => 'username',
                'label'=> 'Username'
            ],
            null,
            function ($value) {
                $this->crud->addClause('where', 'username', 'LIKE', "%$value%");
            }
        );
      // ...
    }
}

text.blade.php

<!-- resources/views/vendor/backpack/crud/filters/text.blade.php -->

<li filter-name="{{ $filter->name }}"
    filter-type="{{ $filter->type }}"
    class=" {{ Request::get($filter->name)?'active':'' }}">
    <span style="display: inline-block;">{{ $filter->label }}</span>
    <input type="text" name="{{ $filter->name }}" style="width: 150px;" />
</li>

@push('crud_list_scripts')
<script>
    jQuery(document).ready(function($) {
        $("input[name={{ $filter->name }}]").keyup(debounce(function(e) {
            e.preventDefault();

            var value = $(this).val();
            var parameter = '{{ $filter->name }}';

            @if (!$crud->ajaxTable())
            // behaviour for normal table
            var current_url = normalizeAmpersand("{{ Request::fullUrl() }}");

            var new_url = addOrUpdateUriParameter(current_url, parameter, value);

            // refresh the page to the new_url
            new_url = normalizeAmpersand(new_url.toString());
            window.location.href = new_url.toString();
            @else
            // behaviour for ajax table
            var ajax_table = $("#crudTable").DataTable();
            var current_url = ajax_table.ajax.url();

            var new_url = addOrUpdateUriParameter(current_url, parameter, value);

            console.log(current_url, new_url);

            // replace the datatables ajax url with new_url and reload it
            new_url = normalizeAmpersand(new_url.toString());
            ajax_table.ajax.url(new_url).load();

            // mark this filter as active in the navbar-filters
            if (URI(new_url).hasQuery('{{ $filter->name }}', true)) {
                $("li[filter-name={{ $filter->name }}]").removeClass('active').addClass('active');
            }
            else
            {
                $("li[filter-name={{ $filter->name }}]").trigger("filter:clear");
            }
            @endif
        }));

        // clear filter event (used here and by the Remove all filters button)
        $("li[filter-name={{ $filter->name }}]").on('filter:clear', function(e) {
            $("li[filter-name={{ $filter->name }}]").removeClass('active');
            $("input[name={{ $filter->name }}]").val('');
        });
    });
</script>
@endpush