Counting bookmarks in Acrobat DC?

This code should do the trick:

function CountBookmarks(bkm) {
   if (bkm.children != null)
        for (var i = 0; i < bkm.children.length; i++) {
            counter++;
            CountBookmarks(bkm.children);
        }
}
var counter = 0;
CountBookmarks(this.bookmarkRoot);
console.println("Number of bookmarks in this file: "+counter);