Remove the extra single quotes around the url and check for the length of the locations array:
$.ajax({
type: "POST",
url: "http://open.mapquestapi.com/geocoding/v1/address?key=012",
data: { location: ad, maxResults: 1}
})
.done(function( response ) {
alert(response.results[0].locations.length); //if greater than zero, you have results
if( response.results[0].locations.length > 0 ){
var geoclng = response.results[0].locations[0].latLng.lng;
var geoclat = response.results[0].locations[0].latLng.lat;
//now use lon/lat on map etc
} else {
alert("Sorry, wrong input");
}
)}
When you run a call to http://open.mapquestapi.com/geocoding/v1/address?key=012, it is going to return an object whether or not there were matches. The contents of that object's locations array will be empty is nothing was found.
response.length == 0
or response == ""
will evaluate to false
since there is always a response returned.