Create custom list from main list in javascript

Question

I have a list object like below

[{a:"0"},{a:"1"},....{a:"39"}]

I want to have a list like the one below.I need a result like the below.

{
  "list1":[{a:"0"},{a:"1"},{a:"2"},{a:"3"}],
  "list2":[{a:"4"},{a:"5"},{a:"6"},{a:"7"}],
  .
  .
  .
  "list10":[{a:"36"},{a:"37"},{a:"38"},{a:"39"}],
}

Thanks for help me.

Is there a reason why you want an object as your output and not an array? Since your object seems to be using sequential keys it looks like an array might be better suited (which then you can use a [chunking method](https://stackoverflow.com/q/8495687/5648954)) — Nick Parsons, Dec 07 '21 at 08:07

score 1 · Answer 1 · answered Dec 07 '21 at 09:02

You can use below code:

const items = [{a: "0"}, {a: "1"}, {a: "2"}, {a: "3"}, {a: "4"}, {a: "5"}, {a: "6"}, {a: "7"}, {a:"8"}, {a:"9"}, {a:"10"}];
let newItems = {};
let i = 1;
while(items.length){
    newItems[`list${i}`] = items.splice(0,4);
    i++;
}
console.log(newItems)

If you want too kep the items immutable you can copy it into another array before while loop, like this const copyItems = [...items] and using copyItems in while.

score 0 · Answer 2 · answered Dec 07 '21 at 08:16

You can use a reduce to achieve this

const items = [{ a: "0" }, { a: "1" }, { a: "2" }, { a: "3" }, { a: "4" }, { a: "5" }, { a: "6" }, { a: "7" }];
items.reduce((accum, curr, index) => {
  const key = `list${1 + Math.floor(index / 4)}`;
  accum[key] = accum[key] || [];
  accum[key].push(curr);
  return accum;
}, {});

score 0 · Answer 3 · answered Dec 07 '21 at 08:16

I believe this might be what you're looking for. This will split the big array into smaller ones and store each array with a size of 4 in the arrayOfArrays.

var bigarray = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];
var size = 4; var arrayOfArrays = [];
for (var i=0; i<bigarray.length; i+=size) {
  arrayOfArrays.push(bigarray.slice(i,i+size));
}
console.log(arrayOfArrays); // [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15]]

score 0 · Accepted Answer · answered Dec 07 '21 at 08:22

0

You can do that using slice() data...

const arr = [{a:"0"},{a:"1"},{a:"2"},{a:"3"},{a:"4"},{a:"5"},{a:"6"},{a:"7"}];

const arr2 = [];

var i,j;
for (i = 0; i < arr.length; i = i + 4) {
    arr2.push(arr.slice(i, i + 4));
}
    
console.log(arr2);

answered Dec 07 '21 at 08:22

Faheem azaz Bhanej

2,328
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score 0 · Answer 5 · answered Dec 07 '21 at 09:07

var data = [{a:"0"},{a:"1"},{a:"2"},{a:"3"}, {a:"4"},{a:"5"},{a:"6"},{a:"7"},{a:"8"},{a:"9"}]

const sliceData = (data, size) => {
    var result = [];
    for(var i = 0; i < data.length; i += size){
       result.push(data.slice(i, i + size));
   }
  return result;
}

console.log(sliceData(data, 4));

result

[
  [ { a: '0' }, { a: '1' }, { a: '2' }, { a: '3' } ],
  [ { a: '4' }, { a: '5' }, { a: '6' }, { a: '7' } ],
  [ { a: '8' }, { a: '9' } ]
]

A1exandr Belan · Answer 6 · 2021-12-07T10:12:14.573

0

Lodash, if you don't mind

Use _.chunk to split array into groups the length of size.

import _ from 'lodash';

data = [{a:"0"},{a:"1"},{a:"2"},{a:"3"}, {a:"4"},{a:"5"},{a:"6"},{a:"7"},{a:"8"},{a:"9"}];
const size = 4;
const result = _.chunk(data, size)
   .reduce((acc, item, index) => ({ ...acc, [`list${index + 1}`]: item }), {});

console.log(result);
//{list1: Array(4), list2: Array(4), list3: Array(2)}

edited Dec 07 '21 at 10:12

answered Dec 07 '21 at 09:55

A1exandr Belan

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Create custom list from main list in javascript

6 Answers6