The code below is for automatically adding a coupon code in the background, on pageload.

fcc.events.cart.ready.add(function(){
    // check for coupon
    $.getJSON('https://' + storedomain + '/cart?output=json' + fcc.session_get() +'&cart=view&callback=?', function(data){
        if (!data.coupons) {
            $.getJSON('https://' + storedomain + '/cart?cart=update&output=json' + fcc.session_get() +'&coupon=free-special-product-shipping&callback=?', function(data){
                // console.log('Coupon added.');
                FC.json = data;
            });
        }
    });
    return true;
});

function fc_BuildFoxyCart() {
// check for coupon
$.getJSON('https://example.foxycart.com/cart?output=json&cart=view&callback=?' + fc_AddSession(),
function(data){
if (!data.coupons) {
$.getJSON('https://example.foxycart.com/cart?cart=update&output=json&coupon=free-special-product-shipping&callback=?' + fc_AddSession(), function(data){
fc_json = data;
});
}
 
});
 
return true;
}

For further details, please see the forum link below.

• https://forum.foxycart.com/discussion/1993