This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
idleRequired: A boolean that determines whether synchronization is allowed when the user agent's device is idle. The default is false.
maxDelay: The maximum delay in milliseconds before the next sync event (or the first sync event if it is periodic). The default is 0, meaning there is no maximum delay.
minDelay: The minimum delay in milliseconds before the next sync event (or the first sync event if it is periodic). The default is 0.
minPeriod: The minimum time in milliseconds between periodic sync events. The default is 0, meaning events are not periodic.
minRequiredNetwork: The network condition under which background synchronization will occur. Valid values are 'network-any', 'network-offline', 'network-online', 'network-non-mobile'. The default value is 'network-online'.