Bl.ocks (pronounced Blocks) is a simple viewer for sharing code examples hosted on GitHub Gist (https://gist.github.com/). As D3 examples are predominantly visualization examples, which can run on any browser, bl.ocks takes codes hosted on GitHub Gist and presents it in a more user-friendly way so users and developers can immediately see the resulting visualization output and the corresponding snippets, without the need to open or download any files.

Bl.ocks can be accessed via http://bl.ocks.org and shows you a minimalistic view of a collection of available projects:

You can view the full gallery of http://bl.ocks.org by going on the official d3 gallery page on GitHub at https://github.com/d3/d3/wiki/Gallery.

The good thing about those open source projects in D3 is the illustration that almost anything is possible to visualize using JavaScript, and it demonstrates how powerful the programming language is. Furthermore, the fact that you don't need to download and deploy code to see the result is a compelling asset, not only of JavaScript but also of D3.js. 

The downside to all of this is that the examples are not integrated with Qlik Sense, and it is up to you to take snippets of D3.js code and incorporate them within your Qlik Sense extension and the Qlik APIs. It requires a bit of a learning curve to get up to speed with comfortably doing so but, eventually, it can become your source of powerful visualizations which, as we have mentioned several times already in this book, takes the possibilities of the Qlik platform on to another level.

Always remember to try to fully understand the code you are taking over from another open source project, as it will be up to you to support the code and the integration going forward.