alexkhismatulin

const items = [1, 2, 3]

try {
  // you need a semicolon after following line to make it work
  items.shift()
  (items.length && items[0] === 2) && items.unshift(1)
} catch(e) {
  console.error(e)
}

alexkhismatulin

const groupBy = (arr, path) => {
  if (!path || typeof path !== "string") return {}

  return Object.keys(arr).reduce((accum, key) => {
    const value = getProperty(arr[key], path)

    if (accum[value]) return { ...accum, [value]: [...accum[value], arr[key]] }

    return { ...accum, [value]: [arr[key]] }
  }, {})

alexkhismatulin

const getProperty = (obj, path, defaultValue) => {
  const tokens = path.split(/[.[\]]+/g).filter(Boolean)

  if (!obj || typeof obj !== "object") return defaultValue

  if (tokens.length === 1) {
    return (obj[tokens[0]] === undefined) ? defaultValue : obj[tokens[0]]
  }

  return getProperty(obj[tokens[0]], tokens.slice(1).join("."), defaultValue)

alexkhismatulin

const match = (fields, key) => {
  if (["string", "number"].indexOf(typeof fields) !== -1) return fields === key
  if (fields.indexOf) return fields.indexOf(key) !== -1

  return false
}

const omit = (obj, fields) => Object.keys(obj).reduce((accum, propName) => {
  if (match(fields, propName)) return accum
  return { ...accum, [propName]: obj[propName] }

alexkhismatulin

const isObject = value => typeof value === "object"

const cloneDeep = (value) => {
  if (!value || !isObject(value)) return value

  if (Array.isArray(value)) return value.map(item => cloneDeep(item))

  return Object.keys(value).reduce((accum, propName) => {
    const propValue = value[propName]