Update related list with change in list in CakePHP 3 - ajax

Question

I have two tables categories and subcategories where categories hasMany subcategories relation.
I have another table products which is related to categories and subcategories.
In add method of products I want to select category from the list and then subcategory associated with particular category selected.
echo $this->Form->input('category_id', ['options' => $categories, 'empty' => true]);
echo $this->Form->input('subcategory_id', ['options' => $subcategories]);
echo $this->Form->input('product_type_id', ['options' => $productTypes]);
echo $this->Form->input('title');
As there is no js helper in CakePHP 3. How could I do this using Ajax.
I'm new to CakePHP and Ajax as well. And currently this show all subcategories in the list.

Answer 1

I get it working like this and its working fine.
view file contain
<?= $this->Form->input('categories', ['options' => $categories, 'empty' => 'Select', 'id' => 'categories']) ?>
<?= $this->Form->input('subcategory_id', ['type' => 'select', 'id' => 'subcategories]) ?>
and myAjax.js file contain
$('#categories').change(function () {
var dataSet = {category_id: $(this).val()};
var requestUrl = appBaseUrl+'products/ajax-subcategories';
$.ajax({
type: "POST",
url: requestUrl,
data: dataSet,
success: function(result) {
$('#subcategories').html(result);
},
error: function(jqXHR, textStatus, errorThrown) {
console.log(textStatus, errorThrown);
}
});
});
and ajaxSubcategories action inside ProductsController.php
public function ajaxSubcategories()
{
$this->autoRender = false;
$this->loadModel('Subcategories');
$category_id = $this->request->data['category_id'];
$subcategories = $this->Subcategories->find()
->where(['category_id' => $category_id, 'deleted' => false, 'status' => 0]);
$data = '';
foreach($subcategories as $subcategory) {
$data .= '<option value="'.$subcategory->id.'">'.$subcategory->title.'</option>';
}
echo $data;
}
Hope this might help someone.