sync.js

var map = client.sync.map('uniqueName');

map.set('foo', { bar: 42 }).then(function() {
  console.log('set it!');
}).catch(function(err) {
  console.log('dang it, dont have access');
});

// same as above...
map.set('foo', { bar: 42 }, function(err) {
  if (err) return console.log('dang it, dont have access');
  console.log('set it!');
});

map.on('value', function(value) {
  console.log('value updated');
});

map.on('error', function(err) {
  if (err.code == 403) {
    console.log('sync failed because you dont have access');
  }
});