checkbox value for Edit not showing as checkbox checked

added these lines in below code but it is showing "checked" first time going to Edit, then on every attempt it is showing it unchecked no matter it is "Y"
please help.
                if($('#product_available').val() == 'Y') {
                    $('#product_available').attr('checked', true);
                }else{
                    $('#product_available').attr('checked', false);
                }



       

PHP Code:

// to fill data in Edit mode
        var subcategorygobal = '';
        $(document).ready(function(){

            // get Edit Product
            $('.btn-edit').on('click',function(){
                // get data for Editing a selected row
                const id = $(this).data('id');
                const name = $(this).data('name');
                const price = $(this).data('price');
                const category = $(this).data('category_id');
                const subcategory = $(this).data('subcategory_id');
                const product_available = $(this).data('product_available');
                // Set data to Form Edit
                $('.product_id').val(id);
                $('.product_name').val(name);
                $('.product_price').val(price);
                $('.product_category').val(category).trigger('change');
                $('.checkboxitem').val(product_available);
// start: code added here...
                if($('#product_available').val() == 'Y') {
                    $('#product_available').attr('checked', true);
                }else{
                    $('#product_available').attr('checked', false);
                }
// end: code added here...
                subcategorygobal = subcategory;
                // Call Modal Edit
                $('#dmlModal').modal('show');
        }); 


regards

Newbie here in CodeIgniter World !! Please appologize if any nonsense from me.  

environment: Windows 10, XAMPP 3.3.0, VS Code, SQLyog Community Ed.