index.ts

/**
 * SPDX-FileCopyrightText: 2019 Nextcloud GmbH and Nextcloud contributors
 * SPDX-License-Identifier: GPL-3.0-or-later
 */

/**
 * @param app app ID, e.g. "mail"
 * @param key name of the property
 * @param fallback optional parameter to use as default value
 * @throws if the key can't be found
 */
export function loadState<T>(app: string, key: string, fallback?: T): T {
	const elem = document.querySelector<HTMLInputElement>(`#initial-state-${app}-${key}`)
	if (elem === null) {
		if (fallback !== undefined) {
			return fallback
		}
		throw new Error(`Could not find initial state ${key} of ${app}`)
	}

	try {
		return JSON.parse(atob(elem.value))
	} catch (e) {
		throw new Error(`Could not parse initial state ${key} of ${app}`)
	}
}