What are some alternatives?
When comparing Gem.js and Vue.js, you can also consider the following products
Svelte - Cybernetically enhanced web apps
AngularJS - AngularJS lets you extend HTML vocabulary for your application. The resulting environment is extraordinarily expressive, readable, and quick to develop.
Preact.js - Preact is a fast 3kB alternative to React with the same modern API. Components & Virtual DOM.
Polymer - Polymer is a library that uses the latest web technologies to let you create custom HTML elements.