I’ve used scratch files in IntelliJ IDEA and Android Studio but I think that can be found in all of Jetbrain’s products.
What are they?
Scratch files are files that don’t get tracked by the version control system, can be created at any given time and, most importantly, get bind to the IDE and not the project that is currently open.
How do I create them?
The simplest way is to hit ctrl+alt+shift+insert. If you can’t remember it press shift twice and start writing scratch, you will be presented with the action of creating a new one.
The next step is to choose what kind of file you want to create and this is where it gets interesting since you can choose from a plethora of file types. From plain text, to markdown, Kotlin, JSON, XML, ruby and many many more!
How do I use them?
By choosing the file’s type you choose how the IDE will behave when you are working on it, so if you create a scratch.json and paste some json in it you can format it accordingly. Or if you create a scratch.md you can start writing in markdown and have a preview of your work.
But the most powerful aspect of those files is when you create code related ones. If, for example, you create a scratch.kts file and start writing some Kotlin in it, you will see your code being run on the fly presenting to you its result:
You can even work test first if you need to figure out a quick algorithm and have your test run in every change you make!
I usually start with an assertThat function and a failing test and go from there: