KnockoutJS!

HTML is great for declaring static documents, but it falters when we try to use it for declaring dynamic views in web-applications. AngularJS lets you extend HTML vocabulary for your application. The resulting environment is extraordinarily expressive, readable, and quick to develop.

Vue.js - Intuitive, Fast and Composable MVVM for building interactive interfaces.

Polymer is a library that uses the latest web technologies to let you create custom HTML elements. Build anything from a button to a complete application as an encapsulated, reusable element that works across desktop and mobile.

You can write less code with Ember's Handlebars integrated templates that update automatically when the underlying data changes.

Build incredible real-time applications in record time. Feathers is a real-time, micro-service web framework for NodeJS that gives you control over your data via RESTful resources, sockets and flexible plug-ins.

Backbone supplies structure to JavaScript-heavy applications by providing models with key-value binding and custom events, collections with a rich API of enumerable functions, views with declarative event handling, and connects it all to your existing application over a RESTful JSON interface.

Sails.js make it easy to build custom, enterprise-grade Node.js apps. It is designed to mimic the MVC pattern of frameworks like Ruby on Rails, but with support for the requirements of modern apps: data-driven APIs with scalable, service-oriented architecture. It's especially good for building chat, realtime dashboards, or multiplayer games.

Forward-thinkingWritten with ES2016. Integrates with Web Components. No external dependencies except polyfills. Leverage the technology of the future but target today's mobile, desktop and browser environments.

WebRx is a browser-based MVVM-Framework that combines Functional-Reactive-Programming with declarative Data-Binding, Templating and Client-Side Routing.

Durandal is a cross-device, cross-platform client framework written in JavaScript and designed to make Single Page Applications (SPAs) easy to create and maintain.