Ask HN: How do you build complex web apps with vanilla JavaScript

Hello everyone, I wanted to ask you how do you learn to build complex web apps by just using javascript? It seems to be a common thing to complain in HN about bloated websites with a heavy use of js and frameworks, for example: https://news.ycombinator.com/item?id=29703546.

Every time I try to build anything more complex than a weather app, my codebase becomes a mess. I'm still very new to software development and I still have a lot to learn, so maybe that's part of the problem. How do you manage your app state, how do you get back your state after a crash or a refresh? All these seem difficult to accomplish without a framework.

Any good courses, blogs, repos to study in order to learn this? Thank you!