If you have no web development experience or it's been a while since you've actively used HTML, CSS or JavaScript, then brush up on the fundamentals using the free tutorials available at http://www.w3schools.com/. If you want something with even more structure, you can also try http://www.asmarterwaytolearn.com/.

Qlik's online help documentation contains a simple tutorial that will help you get familiar with the development environment called the Dev Hub, and the available APIs, as you create your first extension. As of Qlik Sense 2.2, you can find documentation to create visualization extensions, and the tutorial at https://help.qlik.com/en-US/sense-developer/2.2/Content/extend.htm. Make sure that you are looking at the latest version of the documentation by selecting the most current version in the top section of the page. You can also find a similar tutorial by Stefan Walther at GitHub (https://github.com/stefanwalther/qliksense-extension-tutorial).

Review the Qlik Branch blog (http://branch.qlik.com/) and search for extensions at http://www.askqv.com/ to get the latest news about how to use extensions.

There is nothing like live advice from an expert to make sure that you are on the right path. Ralf Becher, who created the extensions used in this chapter, gives online classes on the subject through Q-On Training Center at http://www.q-on.bi/.

Keep it simple and learn to use the most popular open source data visualization JavaScript library D3 (https://d3js.org/). Along with online examples and documentation, you can also find plenty of books on the subject.

Again, keep it simple and choose a D3 chart that looks fun, and then get started developing it. Even if it's an animated chart that ends up being useless in the end, pick something that will motivate you to show it off.

Although it is important that you try to do it yourself first, when you do get stuck, don't hesitate to look over the example extensions found in C:Users<username>DocumentsQlikExamplesExtensions, or the extensions created by fellow developers in Qlik Branch (http://branch.qlik.com/).

Now that you've created the first extension on your own, it's time to give back to the community. As you now know what kind of work is out there in the Qlik Branch (http://branch.qlik.com/), choose your next extension based on what you think would be useful to others and upload it. As well as helping others enrich their data visualization, they help you by testing your extension in different environments and giving you feedback.

Once you have mastered the fundamentals and become a contributor to Qlik Branch, go back to learn anything that you feel would make your development better, such as jQuery, Angular JS, other data visualization JavaScript libraries, or even a predicative analysis JavaScript library.

Find a data analysis need that you cannot directly resolve using Qlik Sense and develop a solution using an extension. This could be a user requirement for a visualization that cannot be created using native chart objects, or a data mining example, such as basket analysis. Once you have a customer that demands certain functionality and you are challenged to deliver a solution, you will quickly become a proficient Qlik Sense developer.