useLocalStorage()

1import {
2  Dispatch,
3  SetStateAction,
4  useCallback,
5  useEffect,
6  useRef,
7  useState,
8} from 'react'
9
10// See: https://usehooks-ts.com/react-hook/use-event-listener
11import { useEventListener } from '../useEventListener'
12
13declare global {
14  interface WindowEventMap {
15    'local-storage': CustomEvent
16  }
17}
18
19type SetValue<T> = Dispatch<SetStateAction<T>>
20
21function useLocalStorage<T>(key: string, initialValue: T): [T, SetValue<T>] {
22  // Get from local storage then
23  // parse stored json or return initialValue
24  const readValue = useCallback((): T => {
25    // Prevent build error "window is undefined" but keep keep working
26    if (typeof window === 'undefined') {
27      return initialValue
28    }
29
30    try {
31      const item = window.localStorage.getItem(key)
32      return item ? (parseJSON(item) as T) : initialValue
33    } catch (error) {
34      console.warn(`Error reading localStorage key “${key}”:`, error)
35      return initialValue
36    }
37  }, [initialValue, key])
38
39  // State to store our value
40  // Pass initial state function to useState so logic is only executed once
41  const [storedValue, setStoredValue] = useState<T>(readValue)
42
43  const setValueRef = useRef<SetValue<T>>()
44
45  setValueRef.current = value => {
46    // Prevent build error "window is undefined" but keeps working
47    if (typeof window == 'undefined') {
48      console.warn(
49        `Tried setting localStorage key “${key}” even though environment is not a client`,
50      )
51    }
52
53    try {
54      // Allow value to be a function so we have the same API as useState
55      const newValue = value instanceof Function ? value(storedValue) : value
56
57      // Save to local storage
58      window.localStorage.setItem(key, JSON.stringify(newValue))
59
60      // Save state
61      setStoredValue(newValue)
62
63      // We dispatch a custom event so every useLocalStorage hook are notified
64      window.dispatchEvent(new Event('local-storage'))
65    } catch (error) {
66      console.warn(`Error setting localStorage key “${key}”:`, error)
67    }
68  }
69
70  // Return a wrapped version of useState's setter function that ...
71  // ... persists the new value to localStorage.
72  const setValue: SetValue<T> = useCallback(
73    value => setValueRef.current?.(value),
74    [],
75  )
76
77  useEffect(() => {
78    setStoredValue(readValue())
79    // eslint-disable-next-line react-hooks/exhaustive-deps
80  }, [])
81
82  const handleStorageChange = useCallback(() => {
83    setStoredValue(readValue())
84  }, [readValue])
85
86  // this only works for other documents, not the current one
87  useEventListener('storage', handleStorageChange)
88
89  // this is a custom event, triggered in writeValueToLocalStorage
90  // See: useLocalStorage()
91  useEventListener('local-storage', handleStorageChange)
92
93  return [storedValue, setValue]
94}
95
96export default useLocalStorage
97
98// A wrapper for "JSON.parse()"" to support "undefined" value
99function parseJSON<T>(value: string | null): T | undefined {
100  try {
101    return value === 'undefined' ? undefined : JSON.parse(value ?? '')
102  } catch {
103    console.log('parsing error on', { value })
104    return undefined
105  }
106}

1import React from 'react'
2
3import { useLocalStorage } from 'usehooks-ts'
4
5// Usage
6export default function Component() {
7  const [isDarkTheme, setDarkTheme] = useLocalStorage('darkTheme', true)
8
9  const toggleTheme = () => {
10    setDarkTheme(prevValue => !prevValue)
11  }
12
13  return (
14    <button onClick={toggleTheme}>
15      {`The current theme is ${isDarkTheme ? `dark` : `light`}`}
16    </button>
17  )
18}