yhtml VS systemjs

The main reason is that they're too low-level to use directly.

They do a lot, but stop just short of being useful without something of a framework on top. I tried hard to use them directly, but found that it was untenable without sensible template interpolation, and without helpers for event binding.

Here's my shot at the smallest possible "framework" atop Web Components that make them workable (and even enjoyable) as an application developer:

https://github.com/dchester/yhtml

It's just ~10 SLOC, admittedly dense, but which make a world of difference in terms of usability. With that in place, now you can write markup in a style not too dissimilar from React or Vue, like...

    ${this.count}

I also sometimes enjoy this approach of starting from absolutely nothing.

Instead of taking the path of starting with DOM manipulation and then going to a framework as necessary, I've kept really trying to make raw web components work, but kept finding that I wanted just a little bit more.

I managed to get the more I wanted -- sensible template interpolation with event binding -- boiled down to a tag function in 481 bytes / 12 lines of (dense) source code, which I feel like is small enough that you can copy/paste it around and not feel to bad about it. It's here if anyone cares to look: https://github.com/dchester/yhtml

I would like to upgrade my existing Rails and Angular 1.x application. I'm following the ng-upgrade documentation and seeing that there are many dependencies including systemjs, typescript, tsd and a few other javascript libraries. Ideally there would be a angular-2 gem that would have all the dependencies but I'm not able to find that. Next I looked for gem's for each dependency but there isn't one for tsd.

There's also https://github.com/systemjs/systemjs if you want more of a ponyfill approach. FWIW bundlers also don't use the browser's functionality to load modules...

A module loader interprets and loads a module written in a certain module format at runtime. Popular examples are RequireJS and SystemJS.