pds-2021-g2-nest/code/frontend/src/hooks/useLocalStorageState.js

import { useCallback, useState } from "react"


/**
 * Hook with the same API as {@link React.useState} which stores its value in the browser's {@link localStorage}.
 */
export default function useLocalStorageState(key, def) {
    /**
     * Load the `key` from the {@link localStorage} into `value`, defaulting to `def` if it is not found.
     */
    const load = () => {
        if(localStorage) {
            console.debug(`Loading ${key} from localStorage...`)
            let _value = JSON.parse(localStorage.getItem(key))

            if(_value) {
                console.info(`Loaded ${key} from localStorage!`)
                return _value
            }
            else {
                console.info(`There is no value ${key} stored, defaulting...`)
                return def
            }
        }
        else {
            console.warn(`Can't load value as localStorage doesn't seem to be available, defaulting...`)
            return def
        }
    }

    const [value, setValue] = useState(load());

    /**
     * Save a value to the {@link localStorage}.
     */
    const save = useCallback(
        (value) => {
            if(localStorage) {
                console.debug(`Saving ${key} to localStorage...`)
                localStorage.setItem(key, JSON.stringify(value))
            }
            else {
                console.warn(`Can't save ${key}; localStorage doesn't seem to be available...`)
            }
        },
        [key]
    )

    /**
     * Set `value` and save it to the {@link localStorage}.
     */
    const setAndSave = useCallback(
        (value) => {
            setValue(value)
            save(value)
        },
        [save]
    )

    return [value, setAndSave]
}