State and persistence

The main page keeps a compact JavaScript state object containing the selected unit, theme, city, and an internal fetch token.

Persisted values

The application uses local storage keys including:

harmattan-unit
harmattan-theme
harmattan-city
harmattan-sound

This means a returning user does not have to reselect the same presentation preferences on every visit.

Defaults

The main page falls back to Celsius, dark theme, and the first city in the curated list. The current first city is Lagos.

Request ordering

fetchToken is an internal stale-response guard. When a newer city request begins, an older response can be ignored instead of overwriting the user's latest selection.

This is useful in a sequence such as:

User selects City A
User quickly selects City B
City B responds first
City A responds later

Without request ordering, the late City A response could incorrectly replace City B.

Persistence boundary

Local storage is browser-local. Preferences do not sync across devices because Harmattan currently has no account system or server-side profile.