Also the modular packages they have built are amazing. They have a node package called @jupyterlab/services which lets you write typescript code for your own libraries that can then call the Jupyter Server.

An example of using JupyterLab services is provided on their GitHub:

https://github.com/jupyterlab/jupyterlab/tree/master/package...

Because of the way they built their packages I have been able to stand on the shoulder of giants and build the following tool:

https://github.com/SimonBiggs/scriptedforms

I am very grateful to the JupyterLab team. They have built something brilliant.