Microsoft recently announced a project called Script Lab, previously known as 'Add-In Playground', which aims to help you learn how to write add-ins for Office.
Script Lab is actually an add-in itself and runs in Excel, Word or PowerPoint and can be installed from the Office Store.
Script Lab will run in Excel, Word, or PowerPoint 2013 Service Pack 1 or later. It also runs on Mac and online versions of these programs. A list of all the supported programs can be found on the Office Store (link above).
Here's Microsoft's promotional video which gives you some idea of what's possible in Script Lab.
So What Can I Do With It?
Well, you can learn to use the Office JavaSctipt API from within Excel (or Word or PowerPoint), and develop add-ins.
The code you write can be run inside Excel and you can see the results in the Task Pane or in the worksheet.
A selection of sample code is provided so you can pick that apart to see how things work.
If you want to contribute to the project, the code for Script Lab is open and waiting for your input.
Installing Script Lab is straight forward, just get it from the Office Store, nothing else is needed.
But, when I installed it to my Excel 2013, I got errors when trying to run the supplied code snippets:
Even though I was running Service Pack 1 for Office 2013, I decided to try reinstalling. That also met with failure:
so I gave up with 2013 and installed it to my laptop running Office 2016 and everything worked fine.
I suspect the sample snippets I was trying to run were specifically built for Office 2016 so wouldn't run in 2013. But this is not made clear anywhere. There is one 2013 sample snippet and that did run without a hitch.
In Excel 2016 you'll find that you have an extra section on your Ribbon
You can also access Script Lab via Insert -> My Add-Ins.
The Template window is where you write your HTML.
CSS goes in the Style window, although this snippet has none, there are still CSS styles used in the HTML and CSS can be imported in the Libraries window.
and you can inspect the DOM (Document Object Model)
As you can see of course, this is all geared towards the web developer and will be familiar with anyone who has built web sites.
Your code snippets can be shared through GitHub. You just send them the link to your code and they can give it a try. Likewise, the Import feature lets you load other people’s snippets.