const chunk = (arr, size) => arr.reduce((acc, e, i) => (i % size ? acc[acc.length - 1].push(e) : acc.push([e]), acc), []);

​

// Examples

chunk([1, 2, 3, 4, 5, 6, 7, 8], 3);     // [[1, 2, 3], [4, 5, 6], [7, 8]]

chunk([1, 2, 3, 4, 5, 6, 7, 8], 4);     // [[1, 2, 3, 4], [5, 6, 7, 8]]

function splitArrayIntoChunksOfLen(arr, len) {

  var chunks = [], i = 0, n = arr.length;

  while (i < n) {

    chunks.push(arr.slice(i, i += len));

  }

  return chunks;

}

var alphabet=['a','b','c','d','e','f'];

var alphabetPairs=splitArrayIntoChunksOfLen(alphabet,2); //split into chunks of two

Array.prototype.chunk = function(size) {

    let result = [];

    while(this.length) {

        result.push(this.splice(0, size));

    }

    return result;

}

​

const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];

console.log(arr.chunk(2));

const splitArray=(arr, chunk)=>{

    const elementInEachSubArray = Math.floor(arr.length / chunk)

    const remainingElement = arr.length - (elementInEachSubArray * chunk)

    let splitArray = Array.from({length: chunk}, ()=>[])

    splitArray = splitArray.map(

        (array, i)=>{

            return arr.slice(i*elementInEachSubArray, elementInEachSubArray * (i + 1))

}

    ).map((array, i)=>[...array, arr[arr.length - remainingElement + i]].filter(Boolean))

    console.log(splitArray)

}