useNewEntries.js

useNewEntries.js

import _ from "lodash"
import { useState, useEffect, useRef } from "react"

export default function useNewEntries({ entries }) {
  const [newEntries, setNewEntries] = useState([])
  const oldEntries = useRef(entries)

  useEffect(() => {
    if (_.isEmpty(entries)) return
    const newEntries = entries.filter(entry =>
      checkIfEntryIsNew({ entry, oldEntries: oldEntries.current })
    )

    setNewEntries(newEntries)

    oldEntries.current = entries
  }, [JSON.stringify(entries)])

  return newEntries
}

function checkIfEntryIsNew({ entry, oldEntries }) {
  if (_.isEmpty(entry)) return false

  const existsAmongOld = (oldEntries || []).some(oldEntry => {
    return JSON.stringify(oldEntry) === JSON.stringify(entry)
  })

  return !existsAmongOld
}