JS contiguous array chunks

contiguous-array-chunks.js

const getChunk = (arr, from, size) => {
  const clampedFrom = (from + size) > arr.length
    // Trying to get chunk bigger than end of array.
    // Here we reduce `from` so that the chunk size is always preserved.
    ? arr.length - size
    : from

  return arr.slice(clampedFrom, from + size)
}

const array = [1,2,3,4,5]
const chunkSize = 2

const result = array
  .map((item, index) => getChunk(array, index, chunkSize))

// This is needed to remove extra pair.
// This pair happens because the result array should be of size equal
// to input.length - 1.
// Example:
// input: [1, 2, 3] (length = 3)
// output: [[1,2], [2,3]] (length = 2)
result.pop()

console.log('result', result)
// result [ [ 1, 2 ], [ 2, 3 ], [ 3, 4 ], [ 4, 5 ] ]

Oops there's a bug of a double item in the end (two 4,5), I'm gonna fix that tomorrow.