script to change single product add to cart text

  add this in addtocart.phtml page

<script>
    require([
        'jquery',
        'mage/mage',
        'Magento_Catalog/product/view/validation',
        'Magento_Catalog/js/catalog-add-to-cart'
    ], function ($) {
        'use strict';
        $('#product_addtocart_form').mage('validation', {
            radioCheckboxClosest: '.nested',
            submitHandler: function (form) {
                var widget = $(form).catalogAddToCart({
                    bindSubmit: false,
                    "addToCartButtonTextDefault": "<?php echo __('IN DEN WACKERKORB'); ?>",
                    "addToCartButtonTextWhileAdding": "<?php echo __('Adding...'); ?>",
                    "addToCartButtonTextAdded": "<?php echo __('Added'); ?>"
                });

                widget.catalogAddToCart('submitForm', $(form));

                return false;
            }
        });
        
        $('.product_quantity_up').click(function(){
            var val = $('#qty').val();
            $('#qty').val( parseInt(val)+1 );
        });
        
        $('.product_quantity_down').click(function(){
            var val = parseInt( $('#qty').val() );
            if( val != 1 )
            {
                $('#qty').val( val-1 );
            }
        });

    });
</script>