Simple algorithm to convert React Native FlatList data to SectionList data

react-native-flastlist-to-sectionlist-data.html

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.20.1/moment.min.js"></script>
<script>
moment.locale();

const data = [
  {
    datetime: "2018-01-03T13:07:46+00:00",
    name: "breakfast"
  },
  {
    datetime: "2018-01-04T00:02:23+00:00",
    name: "dinner"
  },
  {
    datetime: "2018-01-03T17:23:54+00:00",
    name: "lunch"
  },
  {
    datetime: "2018-01-02T05:21:38+00:00",
    name: "dinner"
  },
  {
    datetime: "2018-01-02T17:12:54+00:00",
    name: "lunch"
  },
  {
    datetime: "2018-01-02T06:54:25+00:00",
    name: "breakfast"
  },
  {
    datetime: "2018-01-02T10:39:17+00:00",
    name: "snack"
  },
  {
    datetime: "2018-01-01T12:41:25+00:00",
    name: "dinner"
  },
  {
    datetime: "2017-12-29T18:19:12+00:00",
    name: "breakfast"
  },
  {
    datetime: "2017-12-28T03:55:21+00:00",
    name: "dinner"
  },
  {
    datetime: "2017-12-28T16:44:32+00:00",
    name: "snack"
  },
  {
    datetime: "2017-12-28T01:00:46+00:00",
    name: "breakfast"
  }
]

// Create key param for each object and format datime to locale
let localeData = data.map((item) => {
  item.key = moment(item.datetime).format('YYYY-MM-DD')
  return item
});

// Sort data by datetime
localeData.sort((a,b) => {
  return moment(b.datetime).unix() - moment(a.datetime).unix()
})

// Reduce data for SectionList
const groupedData = localeData.reduce((accumulator, currentValue, currentIndex, array, key = currentValue.key) => {
    const keyObjectPosition = accumulator.findIndex((item) => item.key == key)
    if (keyObjectPosition >= 0) {
      accumulator[keyObjectPosition].data.push(currentValue)
      return accumulator    
    } else {
      return accumulator.concat({ data: [currentValue], key: key })
    }
}, [])

console.log(groupedData)
</script>