TypeScript: Modern JavaScript Development

Adding persistent storage

When the user closes and reopens the app, the user sees an empty list of scans. We can make the list persistent by saving it after a scan and loading it when the app starts. We can use the application-settings module to store the scans. The storage is based on key-value: a value is assigned to a specific key.

Only booleans, numbers, and strings can be stored using this module. An array cannot be stored. Instead, one could store the length under one key (for instance, items-length) and the items under a set of keys (items-0, items-1, ...). An easier approach is to convert the array to a string using JSON.

The list can be saved using the following function:

function save() { applicationSettings.setString("items", JSON.stringify(items)); ...