Ivannnnn

const machine = {
    empty: {
      SELECT: {
      to: 'loading',
      action: (state, dispatch) => {
        interval.stop()
        loadBook().then((book) => dispatch('SELECT_SUCCESS', book))
        return { ...state, title: null, progress: 0 }
      },
    },

Ivannnnn

function usePrevious(value) {
  const ref = useRef()
  useEffect(() => {
    ref.current = value
  }, [value])
  return ref.current
}

Ivannnnn

const blockOne = (funcName) => {
  if (funcName === 'one') {
    return false
  }
}

const emitEvent = (funcName) => {
  console.log('[event] ' + funcName)
}

Ivannnnn

const store = {
  actions: {
    play: (dispatch, payload, actions) => {
      // do some action
      // payload --> 'abc'
      dispatch('play', 'arg1', 'arg2')
    }
  },
  reducer: {
    play: (_) => ({ ..._ })

Ivannnnn

  const audioPlayer = (function () {
    const [state, updateState, watchState] = useState({
      name: 'Ivan',
    })

    watchState({
      name: (name) => {
        console.log('name updated to: ' + name)
      },
    })

Ivannnnn

async function asyncForEach(array, callback) {
  for (let index = 0; index < array.length; index++) {
    await callback(array[index], index, array)
  }
}

const asyncMap = async (arr, cb) =>
  Promise.all(arr.map(async (a, i) => await cb(a, i)))

Ivannnnn

export const classes = (...args) => {
  return args
    .map((arg) => {
      if (arg === null || arg === undefined) return null
      return typeof arg === 'string'
        ? arg
        : Object.keys(arg)
            .filter((key) => arg[key])
            .join(' ')
    })

Ivannnnn

export const newDate = (date, updates) => {
  date = new Date(date)
  Object.keys(updates).forEach((method) => {
    const methodName = 'set' + method.replace(/^\w/, (c) => c.toUpperCase())
    if (!date[methodName]) throw new Error(`Key '${method}' is not supported!`)
    date[methodName](updates[method])
  })
  return date
}

Ivannnnn

function keyBy(collection, key) {
  const result = {}
  collection.forEach(item => result[item[key]] = item)
  return result
}

Ivannnnn

const observe = (el, cb, options = { childList: true }) => {
  const func = mutations => cb(mutations) === false && mo.disconnect()
  const mo = new MutationObserver(func)
  mo.observe(el, options)
}