The java script function for handling submenu expand/collapse 1st checks to see
if the
variable for the submenu name is null; if so the function does nothing.
If the submenu name is not null, the function checks to see if the current
submenu is not the same as the last submenu opened;
if so the old menu is collapsed before expanding the new submenu.
Then the status of the current menu is checked; if open, close. If closed, open.
Finally the menu is saved for comparison when the function is called again.
Code provided in screenshot for study only, hence no copy/paste.
This java script is adapted from
Visual Quickstart Guide CSS, DHTML, and Ajax, Fourth Edition
by Jason Cranford Teague.