I always name my variables descriptive names. For example, if I am in a loop and the variable represents a "record" I will name it record rather than r.
It's much more readable and you're less likely to get name clashes with other functions (r could be lots of things (even in the same file) - render, record, row, red, right)
Personally I have a habit of avoiding that, especially in dynamic languages, because a single typo could have nasty consequences there. So I always figure out a synonym, or use a name for the variable that's either more descriptive:
The dynamic languages I primarily use are TypeScript and Dart. I always have enough type information floating around to catch this kind of thing. But even in JavaScript it wouldn't be much of an issue since it will instantly explode on the first run, which is certainly inconvenient, but nothing major.
It's much more readable and you're less likely to get name clashes with other functions (r could be lots of things (even in the same file) - render, record, row, red, right)