Imports a single page InDesign document into another

indesign_singlepage_replace.jsx

var doc = app.activeDocument;
var docPath = doc.fullName;
var importDoc = app.open(File('~/test_extract.indd'), false);
var pageToImport = importDoc.pages.firstItem();
importDoc.pages.add(LocationOptions.AT_END); // Documents must have at least 1 page
pageToImport.move(LocationOptions.AFTER, doc.pages.firstItem());
doc.pages.item(2).remove();
importDoc.close(SaveOptions.no);