Extensions in Qlik Sense offer the beautiful opportunity to extend your Qlik Sense user experience by creating bespoke data visualizations, objects, or control elements that interact with the powerful Qlik data engine. It's mainly useful when you have a particular use case in mind, or you have seen a great visualization that you would like to implement in Qlik to visualize your data. Furthermore, sometimes advanced use cases exceed the native capabilities of Qlik Sense and require you to introduce custom objects to facilitate some niche requirements.

Luckily, with Qlik Sense and a basic knowledge of web development, this is not very difficult to achieve, and, with a little bit of practice, the possibilities on top of the Qlik Engine have no limits. To get you there, you have so far in this book internalized the basic concepts of web development, which will be vital to understanding this chapter. As such, it will not go into too much detail on how and why the code is used in specific ways. It will focus more on actually introducing you to web development but within Qlik Sense, bringing the structure of a Qlik extension closer to you and deepening your knowledge of Qlik APIs, in particular, the Extension API.

In detail, this chapter will cover the following relevant aspects:

• Structuring the code of your extension project
• Best practice and the dos and don'ts of extending your Qlik Sense apps
• Designing and creating a user-friendly property panel to change the settings of your charts dynamically
• The details of a qHyperCube structure, its definition, and the returned results
• A step-by-step guide to creating a D3 bar chart example from scratch
• A step-by-step guide to creating a drop-down component example from scratch for selecting filter values
• Introduction to some platforms where you can find useful and open source code for your projects