JavaScript: Use a dropdown to change visibility of other fields

Question

Hello
I'm new here and hope you can help me.
I have no JavaScript experience. I've tried a lot, but it doesn't work so far.
I use Adobe Acrobat X (Version 10.1.9).
My idea:
A User should select his country in a dropdown. Depending on the user's selection, appears another dropdown. If no country is selected, no other dropdown is visible.
When the user select the country "England" the dropdown "EnglandAreas" should get visible.
When the user select the country "Scotland" the dropdown "ScotlandAreas" should get visible.
etc
Now I think there are two ways.
1. For each country it has an own area dropdown. When the user opens the document, all area dropdowns are hidden. The User select his country and a JavaScript set the correct area dropdown visible.
2. For all countries there is one area dropdown. When the user opens the document, the area dropdown is hidden. The User select his country and a JavaScript fills the area data of the selected country in the area dropdown and set the area dropdown visible.
Which method makes more sense or is there a third method?
One of my non-working code (try method 1):
var co = this.getField("Country");
var aren = this.getField("AreaEN");
if (co== "England") {
event.value = (aren.display = display.visible)
} else {
event.value = (aren.display = display.hidden)
Thanks for all the help.

Answer 1

Where is that code placed, exactly? It should be something like this:
// Get a field value and a field object
var co = this.getField("Country").valueAsString;
var aren = this.getField("AreaEN");
// Set the visibility of the AreEN field based on the selected value
if (co == "England") {
    aren.display = display.visible;
} else {
    aren.display = display.hidden;
But the correct code does depend on where it's placed.