The parent is talking about an integrated environment for development, where that integrated environment is indistinguishable from the language itself.
Examples of this include elisp and emacs, smalltalk and squeak, and to a lesser extent visual studio and C#.
There have been relatively few ecosystems so integrated. Java and Javascript/html/electron apps are notably not like that at all. There is no one "the" environment for coding those, simply several very popular ones.
My own take is that Apple should have made a "Hypercard"-like thing the "top layer" of a new operating system. In other words, the entire desktop/windows/buttons interface to the main OS would be itself scripted in Hypercard.
Smalltalk takes this a step further of course by making the whole operating system a live environment. The very UI vocabulary one uses can also double as "programming"
Hmm. Unity scripting sort of works like this if you if ignore the closed source parts. It's kind of nice to edit the editor.
At the same time, having the power to corrupt your runtime is arguably more trouble than it's worth.
Examples of this include elisp and emacs, smalltalk and squeak, and to a lesser extent visual studio and C#.
There have been relatively few ecosystems so integrated. Java and Javascript/html/electron apps are notably not like that at all. There is no one "the" environment for coding those, simply several very popular ones.