How to display multi-level tree menus in the drop-down list using javascript _ javascript skills

This article mainly introduces how to display a multi-level tree menu in the drop-down list using javascript. it involves some techniques such as defining, constructing, and traversing javascript property menus, and has some reference value, for more information about how to use javascript to display multi-level tree menus in the drop-down list, see the following example. Share it with you for your reference. The details are as follows:

This example shows the hierarchical menu displayed in the drop-down list box. it can be seen on many websites and is very practical. the option in the drop-down list box is to use JS to control the output, if you have a better way to display it without JS, it would be better because menus like this are implemented using JS, which is more or less troublesome.

The running effect is as follows:

The code is as follows:

Multi-level tree menu displayed in the drop-down list