Express.js was built by TJ Holowaychuk, one of the members of core NodeJS project team. A large community backs this framework, therefore it has the advantage of continuous updates and reforms of all the core features. This is a minimalist framework that is used to build a number of mobile applications and APIs.
It is basically an expressive middleware for Node.js that uses generators. The limited use of callbacks makes the generators a more effective methodology of error mitigation.
Hapi is a powerful and robust framework that is used for developing APIs. It was first introduced by Eran Hammer 2011 at Walmart while trying to handle the traffic on black Friday. The well-developed plugin system and various key features such as input validation, configuration-based functionality, implement caching, error handling, logging and more makes the Hapi one of the most preferred frameworks. It is used for building useful applications and providing technology solutions by several large-scale websites such as PayPal, Disney.