How to display the connection page in the javascript directory tree in the iframe

The help.html page contains directory tree code and iframe. I want to realize that when a link in the directory tree is clicked, the corresponding connection page is displayed in the iframe.
Javascript code for directory tree:

A script named: dtree.js is also called to control the display and hiding of its images

iframe code:

The directory tree is as shown in the picture. After clicking, the detailed page will be displayed in the iframe on the right, just like the help page of Windows

Reply content:

The help.html page contains directory tree code and iframe. I want to realize that when a link in the directory tree is clicked, the corresponding connection page is displayed in the iframe.
Javascript code for directory tree:

A script named: dtree.js is also called to control the display and hiding of its images

iframe code:

The directory tree is as shown in the picture. After clicking, the detailed page will be displayed in the iframe on the right, just like the help page of Windows