The package provides an \ifoddpage conditional to determine if
the current page is odd or even. The macro \checkoddpage must
be used direct before to check the page number using a label.
Two compiler runs are therefore required to achieve correct
results. In addition, the conditional \ifoddpageoronside is
provided which is also true in oneside mode where all pages use
the odd page layout.

Homepage:
https://ctan.org/pkg/ifoddpage
