Perhaps something like this, but I dont have enough details to know if this approach will work or not for you. However, it shows how to use objects as key/value stores.
var fetchingStrategies = {
'grooveshark.com': function () {
return 'grooving!';
},
'youtube.com': function () {
return 'youtubing!';
}
};
//execute fetching strategy based on domain
fetchingStrategies['youtube.com']();
Obviously you can replace the hard-coded 'youtube.com' string by a variable that would hold the correct domain for the lookup.