Up to now the development of this was happening behind the screen, not available for the general public. At first with little snippets, test scenarios and try-outs to find the best way to work with this, not only on Windows platforms but also the other platforms like iOS or Android.
Until now the Office JS API’s were mostly limited to Office365 interfaces but not targeting file content. This now is changed, at least for the first and still somewhat limited version.
What this means is that you now get the option to actually interact with the file contents. For now only on Excel en Word and only for a small subset of the Object Model as you know it from VBA and/or VSTO, but it is a start.
As its now open into the public, go ahead, and take a look at the public preview of Office.js API’s in Office 2016 and try some of the samples to get an impression on how this works:
I will go into some more detail in future blog posts. Hopefully a start to get the full object model available but now on multiple platforms!