Store.js has been around since 2010 (first commit! HN discussion!), and is live on tens of thousands of websites - like cnn.com!
For many years v1.x provided basic cross-browser persistent storage, and over time more and more people started asking for additional functionality.
Store.js version 2 is a full revamp with pluggable storage (it will automatically fall back to one that works in every scenario by default), pluggable extra functionality (like expirations, default values, common array/object operations, etc), and fully cross-browser automatic testing using saucelabs.com.
... read the whole story at github.com.