Where the writes still pending when the page goes away are kept until the
next load. Default: the page's localStorage. Null keeps no journal, and
those writes may be lost with the page.
OptionalmigrateFrom
migrateFrom?:null|Storage
Where earlier releases kept the widget's keys, copied once into a
namespace this database has never held. Default: the page's
localStorage. Null copies nothing.
Where the writes still pending when the page goes away are kept until the next load. Default: the page's
localStorage. Null keeps no journal, and those writes may be lost with the page.