Question 265904 in Javascript Question posted in
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Javascript – How to dynamically separate an array into multiple chunks?

The whole idea is to separate one array into multiple chunks.

Given I have an array named "mainlist":

const mainlist = [
  { label: '1' },
  { label: '2' },
  { label: '3' },
  { label: '4' },
  { label: '5' },
  { label: '6' },
  { label: '7' },
  { label: '8' },
  { label: '9' },
]

I have a second array as a reference to produce final chunks of arrays.

const fixedlist = [
  { label: 'f1', position: 3 },
  { label: 'f1', position: 5 },
]

I simply want to separate items from a mainlist based on each item’s position from fixedItems list.

const output = {
  list1: [
    { label: '1' },
    { label: '2' },
  ],
  list2: [
    { label: '3' },
    { label: '4' },
  ],
  list3: [
    { label: '5' },
    { label: '6' },
    { label: '7' },
    { label: '8' },
    { label: '9' },
  ],
}

There are different scenarios to take into consideration, given there are only 2 loops:

  1. for the first loop it should start slicing the array from the beginning till position - 1. in our case it’s 2. It should automatically create a new array with fields.slice(0, 2)
  2. it also checks if if previous item exists, and if so, if there is a gap between previous item position and the current one. In first occurence there is not, but on the second one there is position 5 - position 3 = 2, which means it should create a new list with 2 elements starting from the last one until the current one.
  3. if current loop is the last one, and there are still items left after it’s position, it should add them to new array list
Tags:

2

Answers


  1. 0

    After some reasoning I think you want to add those "fixed" markers into the list by their position which will split it to sublists. The trick is to first place the markers, then pour in all the rest. Lists of length 0 are ignored.

    const fields = [{ label: '1' }, { label: '2' }, { label: '3' }, { label: '4' }, { label: '5' }, { label: '6' }, { label: '7' }, { label: '8' }, { label: '9' }];
const fixedItems1 = [{ label: 'fixed 1', position: 3 }, { label: 'fixed 2', position: 4 }];
// const fixedItems2 = [{ label: 'fixed 1', position: 3 }, { label: 'fixed 2', position: 5 }];

const MARKER = "MARKER"

function combineListWithMarkers(list, markers) {
  const combinedList = [];

  var offset = 1
  for (let i = 0; i < list.length; i++) {
    if (markers.some(item => item.position == i + offset)) {
      combinedList.push(MARKER)
      offset += 1
    } else {
      combinedList.push(list[i]);
    }
  }

  return combinedList;
}


// ChatGPT
function splitArray(arr, splitElement) {
  const result = [];
  let currentChunk = [];

  for (const item of arr) {
    if (item === splitElement) {
      result.push(currentChunk);
      currentChunk = [];
    } else {
      currentChunk.push(item);
    }
  }

  if (currentChunk.length > 0) {
    result.push(currentChunk);
  }

  return result;
}

const combinedList = combineListWithMarkers(fields, fixedItems1);
const splitted = splitArray(combinedList, MARKER)
const filtered = splitted.filter(item => item.length)
const objectified = filtered.reduce(function(agg, item, index) {
  agg["list" + (index + 1)] = item
  return agg
}, {})
console.log(objectified)
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  2. 0 
    const fields = [{ label: '1' }, { label: '2' }, { label: '3' }, { label: '4' }, { label: '5' }, { label: '6' }, { label: '7' }, { label: '8' }, { label: '9' }];
const fixedItems1 = [{ label: 'fixed 1', position: 3 }, { label: 'fixed 2', position: 4 }];
// const fixedItems2 = [{ label: 'fixed 1', position: 3 }, { label: 'fixed 2', position: 5 }];

const MARKER = "MARKER"

function combineListWithMarkers(list, markers) {
  const combinedList = [];

  var offset = 1
  for (let i = 0; i < list.length; i++) {
    if (markers.some(item => item.position == i + offset)) {
      combinedList.push(MARKER)
      offset += 1
    } else {
      combinedList.push(list[i]);
    }
  }

  return combinedList;
}


// ChatGPT
function splitArray(arr, splitElement) {
  const result = [];
  let currentChunk = [];

  for (const item of arr) {
    if (item === splitElement) {
      result.push(currentChunk);
      currentChunk = [];
    } else {
      currentChunk.push(item);
    }
  }

  if (currentChunk.length > 0) {
    result.push(currentChunk);
  }

  return result;
}

const combinedList = combineListWithMarkers(fields, fixedItems1);
const splitted = splitArray(combinedList, MARKER)
const filtered = splitted.filter(item => item.length)
const objectified = filtered.reduce(function(agg, item, index) {
  agg["list" + (index + 1)] = item
  return agg
}, {})
console.log(objectified)
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