How to add Checkout Custom Form Validation using knockout JS in Magento 2

The knockout JS is one of the biggest change ever introduced in Magento 2 frontend which can be a little hard but it comes out as a really useful tool. Basically, Knockout JS is nothing but one kind of Javascript library that uses the MVVM pattern to bind data to certain DOM elements. In your Magento source code, we usually define a View-Model and a Template and the data bound to the Magento 2 view-model which means whenever any data changes happen to view-model changes, it reflects the template too.

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