Slice Array into an array of arrays

Question

If I have a function:

function sliceArrayIntoGroups(arr, size) {
  var slicedArray = arr.slice(0, size);

  return slicedArray;
}

I am looking to take an array and slice it into an array of arrays.. how would I go about doing so?

So if I had this:

sliceArrayIntoGroups(["a", "b", "c", "d"], 2);

The result should be:

[["a","b"],["c","d"]]

But I don't know how to save the second part of the original array after slicing it.

Any help is appreciated.

This looks like array chunking and I should recommend to you this: locutus.io/php/array/array_chunk — Mike
– Mike, Commented Jan 31, 2017 at 18:20

RomanPerekhrest · Accepted Answer · 2017-01-31 19:03:48Z

7

The solution using regular while loop and custom step parameter:

function sliceArrayIntoGroups(arr, size) {
  var step = 0, sliceArr = [], len = arr.length;
  while (step < len) {
    sliceArr.push(arr.slice(step, step += size));
  }
  return sliceArr;
}

console.log(sliceArrayIntoGroups(["a", "b", "c", "d"], 2));
console.log(sliceArrayIntoGroups(["a", "b", "c", "d", "e", "f"], 2));
console.log(sliceArrayIntoGroups(["a", "b", "c", "d", "e", "f"], 3));

step option points to an offset of each extraction(slicing)

edited Jan 31, 2017 at 19:03

answered Jan 31, 2017 at 18:21

RomanPerekhrest

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Comments

Jordan Running · Accepted Answer · 2017-01-31 19:23:46Z

3

This ought to do it. It's a simple recursive function that slices n elements from the beginning of the array and calls itself with the remaining elements.

function sliceArrayIntoGroups(arr, size) {
  if (arr.length === 0) { return arr; }
  return [ arr.slice(0, size), ...sliceArrayIntoGroups(arr.slice(size), size) ];
}

console.log(sliceArrayIntoGroups([1,2,3,4,5], 2));
console.log(sliceArrayIntoGroups([1,2,3,4,5], 3));
console.log(sliceArrayIntoGroups([1,2,3,4,5], 10));

edited Jan 31, 2017 at 19:23

answered Jan 31, 2017 at 18:16

Jordan Running

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2 Comments

Grizzly Over a year ago

This results in [["a","b","c","d"]]

Jordan Running Over a year ago

@BviLLe_Kid I had my operands reversed. Give it another shot. (When I'm at a computer I'll turn this into a snippet.)

Tiep Phan · Accepted Answer · 2017-01-31 18:22:11Z

2

try this, it will slice origin array to 2 pieces, then concat to 1 array

function sliceArrayIntoGroups(arr, size) {
  if (size >= arr.length || size <= 0) { return arr; }
  return [arr.slice(0, size), arr.slice(size)];
}
console.log(sliceArrayIntoGroups(["a", "b", "c", "d"], 2));

edited Jan 31, 2017 at 18:22

answered Jan 31, 2017 at 18:16

Tiep Phan

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Comments

user2314737 · Accepted Answer · 2017-01-31 18:30:38Z

1

Try this:

 function sliceArrayIntoGroups(arr, size) {
   var result = [];

   while (arr.length > 0) {
     result.push(arr.splice(0, size));
   }

   return result;
 }


 console.log(sliceArrayIntoGroups(["a", "b", "c", "d", "e", "f"], 3));
 console.log(sliceArrayIntoGroups(["a", "b", "c", "d"], 2));

function sliceArrayIntoGroups(arr, size) {
  var result = [];

  while (arr.length > 0) {
    result.push(arr.splice(0, size));
  }

  return result;
}

This will divide array into pieces where each piece will be the size of size variable, so

sliceArrayIntoGroups(["a", "b", "c", "d", "e", "f"], 3);

will output

[["a", "b", "c"], ["d", "e", "f"]]

edited Jan 31, 2017 at 18:30

user2314737

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answered Jan 31, 2017 at 18:20

Luka Kvavilashvili

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1 Comment

Jordan Running Over a year ago

You should note that this code will mutate the original array, which may be unexpected behavior.

Ananth · Accepted Answer · 2017-02-01 06:45:24Z

1

Javascript slice() method returns the selected elements in an array, as a new array object. So using for loop create smallArray and push them to arrGroup array.

function sliceArrayIntoGroups(arr, size) {
  let arrGroup =[];
  for (let i=0; i<arr.length; i+=size) {
    let smallArray = arr.slice(i,i+size);//creating smaller array of required size using slice
    arrGroup.push(smallArray);
  }
  return arrGroup;
}

edited Feb 1, 2017 at 6:45

answered Jan 31, 2017 at 18:37

Ananth

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2 Comments

Joe C Over a year ago

While you may have solved this user's problem, code-only answers are not very helpful to users who come to this question in the future. Please edit your answer to explain why your code solves the original problem.

Ananth Over a year ago

Thanks for the suggestion. Edited the answer.

Adam Jenkins · Accepted Answer · 2017-01-31 18:27:33Z

0

Reduce:

var x = [1,2,3,4,5,6,7,8,9];
var chunk = function(arr,n) {
    var temp;
    return arr.reduce(function(carry,item,index) {

        //if we're at a chunk point: index%n == 0
        if(!(index%n)) { 

            //if temp currently holds items, push it onto carry
            if(temp && temp.length) { carry.push(temp); }

            //reset temp to an empty array
            temp = []; 
        }

        //push the current item onto temp
        temp.push(item);

        //if this is the last item in the array, push temp onto carry
        index == arr.length-1 && carry.push(temp);

        return carry;
    },[]);
};

chunk(x,5);

answered Jan 31, 2017 at 18:27

Adam Jenkins

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