Split at single separator occurrence

Question

I have strings like

A_B_C_D
A_B___C_D

where the ___could be anywhere in the string.

What is the easiest way to split them at any single _ but not at ___?

Answer 1

>>> "A_B_C_D".match(/(?:[^_]|_{2,})+/g)
["A", "B", "C", "D"]

>>> "A_B___C_D".match(/(?:[^_]|_{2,})+/g)
["A", "B___C", "D"]

Instead of finding the separators, we find the components themselves. Notice that the strings must be either non-_'s (because the separator is _), or more than one _s. So the regex to match them is simply like this.

Note that this regex ignores the empty strings if the input starts or ends with _ (e.g. "_a_" will just return ["a"].)