Delete all pages except currently viewed?? Acrobat Javascript

Question

Hello All,
I need to delete all pages in a PDF except the one that is currently being viewed. I thought I had it with this:
var keepPage=this.pageNum
this.deletePages({nStart: keepPage+1, nEnd: this.numPages -1});
var keepPage=this.pageNum
this.deletePages({nEnd: keepPage -1});
But this only works if you are on a page other than the last page.
I appreciate any help.

Answer 1

Thank you so much. I had done this:
var keepPage=this.pageNum
if
(this.numPages -1 > keepPage)
this.deletePages({nStart: keepPage+1, nEnd: this.numPages -1});
var keepPage=this.pageNum
this.deletePages({nEnd: keepPage -1});
Which worked, but would give a:
TypeError: Invalid argument type.
Doc.deletePages:8:App Delete_other_pages:Exec
===> Parameter nEnd.
in the console if you were on page 1.
Yours is clearly done by somebody who knows better. I'll put this in an AcroButton and be in business. Best.