Arcade expressions
Arcade Expressions are used to calculate fields and to customise pop ups (among others). Something to have in mind when using it to calculate fields is that there is not log kept of how the calculation has been done. This means that somehow the code is lost. In that way it is worth keeping snippets of code somewhere else. There is a folder in the he-scratchfolder repository. When using the arcade expressions in pop-ups the code is saved. Thus, sometimes, it might be useful to play with the pop-ups before calculating a field.