Define an array of names in JavaScript:" Joe, Mary, and Mike$33".$ You have to write two functions.

The first function will display the next name, while the second function will display the previous

name. Before displaying the name, the name must be checked if it contains any numbers; if the

name contains any number, the name will not display.

Suppose the span tag used to display the name in HTML code is like this:

Please note that you cannot use jQuery or any external library.

It is important to explain each line of code in detail.