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.

Backbone.js is described as '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' and is a software framework in the development category. There are more than 50 alternatives to Backbone.js, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac and Self-Hosted apps. The best Backbone.js alternative is Vue.js, which is both free and Open Source. Other great sites and apps similar to Backbone.js are React, Angular, Svelte and Vite.
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.

A non-opinionated, totally customizable JavaScript framework designed for writing programs that scale across any platform.
MVC framework making it easy to write realtime, collaborative applications that run in both Node.js and browsers.
Aurelia is a JavaScript client framework that leverages simple conventions to empower your creativity.

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.
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.
The Famous Engine is a free and open source JavaScript rendering engine. What makes the Famous Engine unique is its JavaScript rendering engine and 3D physics engine that gives developers the power and tools to build native quality apps and animations using pure JavaScript.
Both Knockout.js and Backbone.js have their strengths and weaknesses, but together they are amazing! With Knockback.js, you can use the strong ORM provided by Backbone and create dynamic views using Knockout bindings.
Ractive.js is a template-driven UI library that transforms your templates, styles and logic into blueprints for highly interactive apps. Ractive.js works for you, not the other way around. You do not need to learn new terminologies, concepts, and methodologies.
Free web application framework for building Web sites and Web applications using JavaScript, HTML and CSS.
Harp is a production-ready web server. Rapidly build static sites and client-side applications using , and more—no configuration necessary.
The Harp Platform is the easiest way for anyone to create an exceptional website. Landing Pages, galleries, blogs, e-commerce, domains, hosting, analytics, 24/7 support - all included.