seo-rich-snippets-availability-alteration.html

<script data-cfasync="false">   
/*
    Web Site Advantage: SEO Rich Snippets Availability Alteration [v1.0] 
    Change a products availability based on specific stock levels
    https://bigcommerce.websiteadvantage.com.au/rich-snippets/
    Copyright (C) 2023 Web Site Advantage
*/

// place this in the footer

{{~#if page_type '===' 'product'}}

var stockLevel = '{{product.stock_level}}';

if (stockLevel == '999') {
    updateAvailability('PreOrder');
}

function updateAvailability(newValue) {
    var element = document.getElementById('wsa-rich-snippets-jsonld-product');

    var json = JSON.parse(element.text);

    if (json.offers) {
        for(var i=0; i < json.offers.length; i++) {
            var offer = json.offers[i];

            if (offer.availability) {
                offer.availability = newValue;
            }
        }
    } 
    element.text = JSON.stringify(json);
}

{{~/if}}
</script>