Recently I needed to deploy an Azure Data Lake Store - Gen 2 instance and thought I'd take the opportunity to use some custom ARM template functions. These aren't something you often see in the example templates but can be really useful if there's a complex expression which you find yourself writing repeatedly within a template.
If, for instance, you routinely create resource names based on a prefix, unique name and a suffix then this could save you a few keystrokes. In essence you are simply parameterizing the expression as follows:
An ARM function in VS Code
In this way you can use this simpler expression where you would have previously used the more complex version.
If you want to see what this looks like in a full template then checkout this simple ARM template I put together for creating a Data Lake Store - Gen 2 instance over on GitHub.