Hi,

1./** @odoo-module */

import { PaymentScreen } from "@point_of_sale/app/screens/payment_screen/payment_screen";

import { patch } from "@web/core/utils/patch";

patch(PaymentScreen.prototype, {

    async validateOrder(isForceValidate) {

        //Add your code

        await super.validateOrder(...arguments);

    },

});

2. Add your js file in Correct asset bundle.

    'assets': {

        'point_of_sale._assets_pos': [

          //Add your file

        ],

     },

Hope it helps