useLocalStorage()

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

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}