A single page is also part of a spread, a single paged spread.
To answer your question you can see if there's more pages in the spread which is the parent of the page. If's there's only one page in the spread then it's a single page spread.
isSinglePageSpread = myPages.parent.pages.length === 1;
Do you plan to know where a page is in the printed, bound and folded document?
Or do you like to know where the page is positioned in the document relative to the spine?
Some cases below.
Every line is a spread.
Every number is a page number in the order of the document:
documentOffset + 1
A. Facing pages document, pageBinding LEFT_TO_RIGHT
2 | 3
4 | 5
B. Facing pages document, pageBinding RIGHT_TO_LEFT
3 | 2
5 | 4
C. Facing pages, pageBinding LEFT_TO_RIGHT with fold out
2 | 3
4 | 5 - 6
7 - 8 | 9
10 | 11
D. Non-facing pages document
E. Non-facing pages document ( one spread ):
D. Non-facing pages document where pages are moved ( one spread ):
There are more variations possible.
First check, if there is a spine:
will return true or false
If false, there is no spine => non-facing pages document.
Then check, if the pages order is LTR or RTL:
app.documents.documentPreferences.pageBinding /* Can return: DEFAULT_VALUE LEFT_TO_RIGHT RIGHT_TO_LEFT */