AppleScript: Hide all applications and show the desktop on Mac

hide-all-app.scpt

tell application "Finder"
    set visible of every process whose visible is true and name is not "Finder" to false
    set the collapsed of windows to true
end tell

launch-an-app.scpt

set appName to "Mail"
set startIt to false
tell application "System Events"
    if not (exists process appName) then
        set startIt to true
    else if frontmost of process appName then
        set visible of process appName to false
    else
        set frontmost of process appName to true
    end if
end tell
if startIt then
    tell application appName to activate
end if