@toolpad/utils/modern/hooks/useStorageState.js

Shared utilities used by Toolpad packages.

import * as React from 'react';
import { Emitter } from "../events.js";

// storage events only work across windows, we'll use an event emitter to announce within the window
const emitter = new Emitter();
function subscribe(area, key, cb) {
  const storageHandler = event => {
    if (event.storageArea === area && event.key === key) {
      cb();
    }
  };
  window.addEventListener('storage', storageHandler);
  emitter.on(key, cb);
  return () => {
    window.removeEventListener('storage', storageHandler);
    emitter.off(key, cb);
  };
}
function getSnapshot(area, key) {
  return area.getItem(key);
}
function setValue(area, key, value) {
  if (typeof window !== 'undefined') {
    if (value === null) {
      area.removeItem(key);
    } else {
      area.setItem(key, String(value));
    }
    emitter.emit(key, null);
  }
}
function useStorageStateServer(kind, key, initializer = null) {
  const [initialValue] = React.useState(initializer);
  return [initialValue, () => {}];
}

/**
 * Sync state to local/session storage so that it persists through a page refresh. Usage is
 * similar to useState except we pass in a storage key so that we can default
 * to that value on page load instead of the specified initial value.
 *
 * Since the storage API isn't available in server-rendering environments, we
 * return initialValue during SSR and hydration.
 *
 * Things this hook does different from existing solutions:
 * - SSR-capable: it shows initial value during SSR and hydration, but immediately
 *   initializes when clientside mounted.
 * - Sync state across tabs: When another tab changes the value in the storage area, the
 *   current tab follows suit.
 */

function useStorageStateBrowser(kind, key, initializer = null) {
  const [initialValue] = React.useState(initializer);
  const area = kind === 'session' ? window.sessionStorage : window.localStorage;
  const subscribeKey = React.useCallback(cb => subscribe(area, key, cb), [area, key]);
  const getKeySnapshot = React.useCallback(() => getSnapshot(area, key) ?? initialValue, [area, initialValue, key]);
  const getKeyServerSnapshot = React.useCallback(() => initialValue, [initialValue]);
  const storedValue = React.useSyncExternalStore(subscribeKey, getKeySnapshot, getKeyServerSnapshot);
  const setStoredValue = React.useCallback(value => {
    const valueToStore = value instanceof Function ? value(storedValue) : value;
    setValue(area, key, valueToStore);
  }, [area, key, storedValue]);
  return [storedValue, setStoredValue];
}
export default typeof window === 'undefined' ? useStorageStateServer : useStorageStateBrowser;