1. storageevent api

  2. storageevent api: initstorageevent

  3. storageevent api: key

  4. storageevent api: newvalue

  5. storageevent api: oldvalue

  6. storageevent api: storagearea

  7. storageevent api: `storageevent()` constructor

  8. storageevent api: url