Form Fields hide/show options

In the Directory theme, when setting up the Listing page for users to enter their information, is there some way to configure the form fields so that when you select an answer, dependent on that answer, another field might appear.
For example, if the listing field is “Country”, and someone selects the US, then a list of US States pops open for them to choose their State. Conversely, if they choose Australia as the country, then a list of Australian States would open.
Another example would be if there is an “Other” option on a list and choosing that option results in a test box appearing where they can enter their “other” details.
I think this requires JavaScript to perform this function, but I wondered if there was a plugin or something that could make this happen?