Composition is incredibly powerful, allowing us to stitch together reusable pieces of functionality to “compose” a larger application. Composition ushers in a mindset of things being good when they’re modular, smaller and easier to test. Easier to reason with. Easier to distribute.
From Addy’s excellent survey of the JS landscape for 2015. As a front end developer that got started with JS hacking the ExtJS components built into ColdFusion 8 and moved on to straight up ExtJS applications I definitely experienced the power of composition.