WooCommerce 商品快速結帳按鈕

woocommerce_quick_checkout.php

function mxp_woocommerce_after_add_to_cart_button(){
        global $woocommerce;
        $checkout_url = $woocommerce->cart->get_checkout_url();
        echo '<div id="ks_quick_checkout"><a href="'.$checkout_url.'?add-to-cart='.get_queried_object_id().'" class="button alt">直接結帳</a></div>';
?>
<script>
jQuery(document).ready(function() {
    var v_product = jQuery('form.variations_form.cart').data();
    if (v_product === undefined) {
        return;
    }
    var p_vdata = v_product.product_variations;
    var p_id = v_product.product_id;
    var v_pricing_key = [];
    for (var i = 0; i < p_vdata.length; i++) {
        var e = p_vdata[i];
        var attrs = e.attributes;
        var v_id = e.variation_id;
        var subkey = [];
        for (var key in attrs) {
            var index = key;
            var data = attrs[key];
            if (data != "") {
                vpush = { v_id: v_id, v_v: data, v_key: index, p_id: p_id };
            } else {
                subkey.push(index);
            }
        }
        vpush.sub = subkey;
        v_pricing_key.push(vpush);
    }
    // console.log(v_pricing_key);
    jQuery('#ks_quick_checkout>a').attr('href', 'javascript:');
        jQuery('#ks_quick_checkout').click(function() {
        //掃描現在的選擇
        for (var i = 0; i < v_pricing_key.length; i++) {
            var v = v_pricing_key[i];
            if (jQuery('select[name="' + v.v_key + '"]').val() == "") {
                alert('請先選擇項目！');
                return;
            }
            if (jQuery('select[name="' + v.v_key + '"]').val() == v.v_v) {
                var vkey = decodeURI(v.v_key.split('_').join('_pa_'));
                var checkout_url = '/checkout/?add-to-cart=' + v.p_id + '&variation_id=' + v.v_id + '&' + vkey + '=' + encodeURI(v.v_v) + '&';
                for (var j = 0; j < v.sub.length; j++) {
                    var other_attr = v.sub[j];
                    if (jQuery('select[name="' + other_attr + '"]').val() == "") {
                        alert('請先選擇項目！');
                        return;
                    }
                    checkout_url += decodeURI(other_attr.split('_').join('_pa_')) + '=' + encodeURI(jQuery('select[name="' + other_attr + '"]').val());
                }
                // console.log(checkout_url);
            }
        }
        var form = jQuery('form.variations_form.cart');
        form.attr('action', '/checkout/');
        form.submit();
    });
});
</script>
<?php
}
add_action('woocommerce_after_add_to_cart_button','mxp_woocommerce_after_add_to_cart_button');

Ref: WooCommerce Custom “Add to Cart” URLs – The Ultimate Guide