This is a Magento 2 example that, how can we change magento2 core design or codes.
Here I have used mixin and mapping for .js and .html files. Here .js file is extended to add some js attributes, and .html file is override.
One noticeable point that, to mapped “Magento_Ui/templates” we have to use “ui/template”.
Download link : Change Admin Design (16 downloads) .