The open source nature of WordPress has improved developer engagement to customize and improve existing features by developing plugins, and contributing to the core framework. Inside the core framework, we can find dozens of popular open source libraries and plugins. We planned this chapter to understand the usage of trending open source libraries within the core.

First, we looked at the open source libraries inside the core. Backbone.js and Underscore.js are trending as popular libraries for web development and hence have been included in the latest WordPress version. Throughout this chapter, we looked at the use of Backbone.js inside WordPress while building the developer profile page of the portfolio application. We looked into Backbone.js concepts such as models, collections, validation, views, and events.

Later on, we looked at the usage of existing PHP libraries within WordPress by using PHPMailer to build a custom e-mail sending interface. In web applications, developers don...