JavaScript — Split an array like a string

Question

Is it possible to split an array into smaller arrays each time a specific value is found? In this case, every time type equals "divider".

Input:

[
    {
        "type": "type-a",
        "name": "Foo"
    },
    {
        "type": "type-b",
        "name": "Foo"
    },
    {
        "type": "type-c",
        "name": "Foo"
    },
    {
        "type": "divider",
        "name": "Foo"
    },
    {
        "type": "type-b",
        "name": "Foo"
    },
    {
        "type": "type-b",
        "name": "Foo"
    },
    {
        "type": "divider",
        "name": "Foo"
    },
    {
        "type": "type-c",
        "name": "Foo"
    }
]

Desired output:

[
    [
        {
            "type": "type-a",
            "name": "Foo"
        },
        {
            "type": "type-b",
            "name": "Foo"
        },
        {
            "type": "type-c",
            "name": "Foo"
        }
    ],
    [
        {
            "type": "type-b",
            "name": "Foo"
        },
        {
            "type": "type-b",
            "name": "Foo"
        }
    ],
    [
        {
            "type": "type-c",
            "name": "Foo"
        }
    ]
]

Does this answer your question? break array of objects into separate arrays based on a property — pilchard
– pilchard, Commented Jul 14, 2022 at 12:35
@pilchard I'm not sure that's exactly the same question. The other question is a classic "group by", here's it's a little bit different but I am sure it's been asked before. — customcommander
– customcommander, Commented Jul 14, 2022 at 12:40
This is probably closer to what OP wants — stackoverflow.com/q/34513679/1244884 — customcommander
– customcommander, Commented Jul 14, 2022 at 12:55
@customcommander too true, I didn't look at the dupe closely enough. perhaps: Split an array of objects in to two, based on a value within the object but adapted for multiple divisions, or yours which just needs adapting to objects (a shame findIndex doesn't have a fromIndex param as indexOf does) — pilchard
– pilchard, Commented Jul 14, 2022 at 12:56

pilchard · Accepted Answer · 2022-07-14 12:33:55Z

1

This should work

const arr = [{ "type": "type-a", "name": "Foo" }, { "type": "type-b", "name": "Foo" }, { "type": "type-c", "name": "Foo" }, { "type": "divider", "name": "Foo" }, { "type": "type-b", "name": "Foo" }, { "type": "type-b", "name": "Foo" }, { "type": "divider", "name": "Foo" }, { "type": "type-c", "name": "Foo" }];

function divide(container, divider) {
  const final = [];
  let tmp = new Array();
  for (let item of container) {
    if (item.type === divider) {
      final.push(tmp);
      tmp = new Array();
    }
    item.type !== divider && tmp.push(item)
  }

  tmp.length > 0 && final.push(tmp)
  return final;
}

const res = divide(arr, 'divider');

console.log(res)

edited Jul 14, 2022 at 12:33

pilchard

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answered Jul 14, 2022 at 12:33

Ahmed Gaafer

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Comments

pilchard · Accepted Answer · 2022-07-14 12:32:14Z

0

You can make use of reduce here as:

const arr = [{ "type": "type-a", "name": "Foo" }, { "type": "type-b", "name": "Foo" }, { "type": "type-c", "name": "Foo" }, { "type": "divider", "name": "Foo" }, { "type": "type-b", "name": "Foo" }, { "type": "type-b", "name": "Foo" }, { "type": "divider", "name": "Foo" }, { "type": "type-c", "name": "Foo" }];

const temp = [];
const result = arr.reduce((acc, curr) => {
  if (curr.type === 'divider') {
    acc.push([...temp]);
    temp.length = 0;
  } else {
    temp.push(curr);
  }
  return acc;
}, []);
if (temp.length) result.push([...temp]);

console.log(result);

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edited Jul 14, 2022 at 12:32

pilchard

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answered Jul 14, 2022 at 12:30

DecPK

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Comments

Apostolos · Accepted Answer · 2022-07-14 12:30:01Z

0

Try this. Search each object of the array and till you find the divider one, push all the objects into another array.

If divider is found, then increment the index, ignore this object and continue.

let arr=[{"type":"type-a","name":"Foo"},{"type":"type-b","name":"Foo"},{"type":"type-c","name":"Foo"},{"type":"divider","name":"Foo"},{"type":"type-b","name":"Foo"},{"type":"type-b","name":"Foo"},{"type":"divider","name":"Foo"},{"type":"type-c","name":"Foo"}]

let finalArr = []
let currentIndex = 0;

for (let obj of arr) {
  if (obj.type === 'divider') {
    currentIndex++;
  } else {
    (finalArr[currentIndex] = finalArr[currentIndex] || []).push(obj);
  }
}

console.log(finalArr)

answered Jul 14, 2022 at 12:30

Apostolos

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Comments

customcommander · Accepted Answer · 2022-07-14 21:04:51Z

Here's a curried recursive function:

The first parameter is a predicate function that takes an element and decides whether that element is a delimiter. Then it takes an array and splits it into chunks. Each chunk contains the elements in between (but excluding) a delimiter element.

const splitBy = pred => function loop([x, ...xs], ret = [[]]) {
  if (x == null) return ret;
  if (pred(x)) ret.push([]);
  else ret[ret.length-1].push(x);
  return loop(xs, ret);
}

const isDivider = x => x.type == 'divider';
const splitByDivider = splitBy(isDivider);

splitByDivider([ { "type": "type-a" , "name": "Foo" }
               , { "type": "type-b" , "name": "Foo" }
               , { "type": "type-c" , "name": "Foo" }
               , { "type": "divider", "name": "Foo" }
               , { "type": "type-b" , "name": "Foo" }
               , { "type": "type-b" , "name": "Foo" }
               , { "type": "divider", "name": "Foo" }
               , { "type": "type-c" , "name": "Foo" }]);

//=> [ [ { "type": "type-a", "name": "Foo" }
//=>   , { "type": "type-b", "name": "Foo" }
//=>   , { "type": "type-c", "name": "Foo" } ]
//=> , [ { "type": "type-b", "name": "Foo" }
//=>   , { "type": "type-b", "name": "Foo" } ]
//=> , [ { "type": "type-c", "name": "Foo" } ]]

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