I have worked in vROps which is a web-based monitoring application for vCenter servers. The application is based on Java with ExtJS web UI.
I have worked on a tool here to bundle ExtJS scripts in order to optimize script loading and I have optimized it for 6+ times for some network connections (tested on DSL network connection). I was using NodeJS and Gulp for that tool. And in the research process, I also investigated Grunt and Webpack.
I also have worked with Angular 5+ for some separate pages and mocks and also I have worked on an idea of partial Angular integration to that old platform which will help the company to step by step move to Angular.