freesewing/sites/shared/hooks/useLocalStorage.mjs

import { useState, useEffect, useRef, useReducer } from 'react'

// See: https://usehooks.com/useLocalStorage/
export function useLocalStorage(key, initialValue, reducer) {
  const prefix = 'fs_'
  const [storedValue, setStoredValue] =
    typeof reducer == 'function' ? useReducer(reducer, initialValue) : useState(initialValue)
  // use this to track whether it's mounted. useful for doing other effects outside this hook
  const [ready, setReady] = useState(false)
  const readyInternal = useRef(false)
  const setValue = setStoredValue

  // set to localstorage every time the storedValue changes
  useEffect(() => {
    if (readyInternal.current) {
      window.localStorage.setItem(prefix + key, JSON.stringify(storedValue))
    }
  }, [storedValue])

  // get the item from localstorage after the component has mounted. empty brackets mean it runs one time
  useEffect(() => {
    readyInternal.current = true
    const item = window.localStorage.getItem(prefix + key)
    let valueToSet = storedValue
    if (item) {
      valueToSet = JSON.parse(item)
    }

    if (reducer) {
      valueToSet = { value: valueToSet, type: 'replace' }
    }

    setValue(valueToSet)
    setReady(true)
  }, [])

  return [storedValue, setValue, ready]
}