Call a method in odoo11 POS after changing customer

There is a widget in the POS(point of sale) called PaymentScreenWidget and inside that there's a customer_changed method which is called when the customer is changed.

There is a widget in the POS(point of sale) called PaymentScreenWidget and inside that there's a customer_changed method which is called when the customer is changed.

Suppose that I want to call a method after this method is called then how can I do this without interfering with this code?

Interfering with this code leaves a lot of trouble in many case so are there any ways to achieve this?

I want to append some text to it but since there are many module who try to change those code or override it I want to avoid doing it and try to call my method after that method has been called.

Difference between AngularJS, React, Ember, Backbone, and Node.js.

The most common thing between all of them is that they are Single Page Apps. The SPA is a single page where much of the information remains the same and only some piece of data gets modified when you click on other categories/option.

What are the differences between the various JavaScript frameworks? E.g. Vue.js, Angular.js, React.js

What are the differences? Do they each have specific use contexts?

What are the differences? Do they each have specific use contexts?