useLocalStorage()

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

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}