Backbone.js

Backbone.js is a lightweight JavaScript library that brings structure to client‐side applications by providing models with key–value binding and custom events, collections with rich enumerable functions, views with declarative event handling, and a router for managing application state and URLs. It syncs seamlessly with RESTful APIs via its built‐in sync method, making it easy to fetch and persist JSON data. By relying only on Underscore.js (and optionally jQuery or Zepto), Backbone.js imposes minimal constraints on how you architect your code while offering just enough conventions to keep large‐scale single‐page applications organized and maintainable. Its event‐driven design encourages decoupled components, and its simplicity has made it popular for developers who prefer to assemble their own toolchains rather than adopt more opinionated frameworks.