Storage

The store/* namespace provides access to the browser's localStorage and sessionStorage APIs. Values are automatically JSON-serialized on write and JSON-parsed on read, so Sema types (strings, numbers, lists, maps) are preserved across storage round-trips.

localStorage

(store/get key) -> value | nil

Retrieve a value from localStorage. Returns nil if the key does not exist or if parsing fails.

(store/get "username")        ;; => "alice"
(store/get "preferences")     ;; => {:theme "dark" :lang "en"}
(store/get "nonexistent")     ;; => nil

(store/set! key value) -> nil

Store a value in localStorage. The value is JSON-serialized.

(store/set! "username" "alice")
(store/set! "count" 42)
(store/set! "todos" [{:text "Buy milk" :done false}])

(store/remove! key) -> nil

Remove a key from localStorage.

(store/remove! "username")

(store/clear!) -> nil

Remove all keys from localStorage.

(store/clear!)

(store/keys) -> list of strings

List all keys currently in localStorage.

(store/keys)  ;; => ("username" "count" "todos")

(store/has? key) -> boolean

Check whether a key exists in localStorage.

(if (store/has? "auth-token")
  (println "Logged in")
  (println "Not logged in"))

sessionStorage

Session storage functions mirror their localStorage counterparts but data is scoped to the browser tab and cleared when the tab closes.

(store/session-get key) -> value | nil

(store/session-get "draft")

(store/session-set! key value) -> nil

(store/session-set! "draft" "Work in progress...")

(store/session-remove! key) -> nil

(store/session-remove! "draft")

(store/session-clear!) -> nil

(store/session-clear!)

Type Preservation

Values are stored as JSON, so the following types round-trip correctly:

Sema Type	JSON Encoding
String	"hello"
Number	42, 3.14
Boolean	true, false
List	[1, 2, 3]
Map	{"key": "value"}
nil	null

Example: Persisting State

;; Save state on change
(define (save-todos! todos)
  (store/set! "todos" todos))

;; Restore state on load
(define (load-todos)
  (or (store/get "todos") []))

;; Usage
(def todos (load-todos))
;; ... modify todos ...
(save-todos! todos)

Error Handling

Storage operations can fail (e.g., quota exceeded, storage disabled in private browsing). Errors are reported to the context's onerror handler and the function returns nil rather than throwing.