What are some alternatives?
When comparing Gem.js and AngularJS, you can also consider the following products
Vue.js - Reactive Components for Modern Web Interfaces
Backbone.js - Give your JS App some Backbone with Models, Views, Collections, and Events
Svelte - Cybernetically enhanced web apps
Preact.js - Preact is a fast 3kB alternative to React with the same modern API. Components & Virtual DOM.