var testSet = new Set(); testSet.add(1); testSet.add(2); chrome.storage.local.set( { \'key\': testSet }, function() { chrome.storage.local.get( \'key\', function(dat
From the chrome API docs:
StorageArea.get(string or array of string or object keys, function callback)
So it looks like you can only use primitives and objects containing primitives.