original.js

// repetitive code!
function selectedLocation() {
  var selected = document.getElementById("countyLocation").value;

  if (selected == "Ireland") {
    var Ireland = new google.maps.LatLng(53.527248, -8.327637);
    map.setCenter(Ireland);
    map.setZoom(6);
  }

  if (selected == "Clare") {
    var Clare = new google.maps.LatLng(52.988337, -9.102173);
    map.setCenter(Clare);
    map.setZoom(8);
  }

  if (selected == "Dublin") {
    var Dublin = new google.maps.LatLng(53.399707, -6.262207);
    map.setCenter(Dublin);
    map.setZoom(9);
  }
}

refactored.js

function selectedLocation() {
  var selected = document.getElementById("countyLocation").value;

  var locations = {
    "Ireland" : {
      lat : 53.527248,
      lng : -8.327637,
      zoom : 6
    },
    "Clare" : {
      lat : 52.988337,
      lng : -9.102173,
      zoom : 8
    },
    "Dublin" : {
      lat : 53.399707, 
      lng : -6.262207,
      zoom : 9
    }
  };

  var location = locations[ selected ];
  var center = new google.maps.LatLng(location.lat, location.lng);
  map.setCenter(center);
  map.setZoom(location.zoom);
}

Nice. Love using hash tables like this, as opposed to switch statements.

A couple of bugs:

• selected should get "countryLocation" instead of "countyLocation" (before and after)
• the locations object should be outside of the function, otherwise it would be created every time the function is called.

I guess that you should test if location isn't undefined before instantiate a new Google Maps LatLng.