Magento 2 - How to detect shipping method change

Question

In Magento 2 I try to track shipping method change in JS.

For exemple when pickup relay is selected I need to display a specific message on frontend.

Do you how can I do this ?

Answer 1

1. Register mixin

app/code/Acme/StackExchange/view/frontend/requirejs-config.js

let config = {
    config: {
        mixins: {
            'Magento_Checkout/js/action/select-shipping-method': {
                'Acme_StackExchange/js/action/select-shipping-method-mixin': true
            }
        }
    }
};

2. Create mixin

app/code/Acme/StackExchange/view/frontend/web/js/action/select-shipping-method-mixin.js

define([
    'mage/utils/wrapper'
], function (wrapper) {
    'use strict';

    return function (selectShippingMethod) {
        return wrapper.wrap(selectShippingMethod, function (_super, shippingMethod) {
            if (shippingMethod) {
                // your logic before shippingMethod set to quote
            }
            _super(shippingMethod);
            if (shippingMethod) {
                // your logic after shippingMethod set to quote
            }
        });
    };
});