De-Chrome-ify helper class directory

src/lib/browser/StorageHelper.js

@@ -0,0 +1,57 @@
+/**
+ * Helper class to read and write JSON objects to the local storage.
+ * @class
+ */
+class StorageHelper {
+  /**
+   * @type {import('@types/chrome').storage.StorageArea}
+   */
+  #storageArea;
+
+  /**
+   * @param {import('@types/chrome').storage.StorageArea} storageArea
+   */
+  constructor(storageArea) {
+    this.#storageArea = storageArea;
+  }
+
+  /**
+   * Read the following entry from the local storage as a JSON object.
+   *
+   * @param {string} key Key of the entry to read.
+   * @param {any} defaultValue Default value to return if the entry does not exist.
+   *
+   * @return {Promise<any>} The JSON object or the default value if the entry does not exist.
+   */
+  async read(key, defaultValue = null) {
+    return (await this.#storageArea.get(key))?.[key] || defaultValue;
+  }
+
+  /**
+   * Write the following JSON object to the local storage.
+   *
+   * @param {string} key Key of the entry to write.
+   * @param {any} value JSON object to write.
+   */
+  write(key, value) {
+    void this.#storageArea.set({[key]: value});
+  }
+
+  /**
+   * Subscribe to changes in the local storage.
+   * @param {function(Record<string, StorageChange>): void} callback
+   */
+  subscribe(callback) {
+    this.#storageArea.onChanged.addListener(callback);
+  }
+
+  /**
+   * Unsubscribe from changes in the local storage.
+   * @param {function(Record<string, StorageChange>): void} callback
+   */
+  unsubscribe(callback) {
+    this.#storageArea.onChanged.removeListener(callback);
+  }
+}
+
+export default StorageHelper;