配列を指定サイズで分割

ライブラリ使わずにやる

• Array.reduce()、spread operator, Array.splice() を組み合わせる

const arr = [...Array(100).keys()];
// => [0, 1, 2, 3, 4, 5, 6, 7, 8,...,99];

const size = 8;

const result = arr.reduce(
  (prev, curr, index) =>
    index !== 0 && index % size !== 0
      ? [...prev.splice(0, prev.length - 1), [...prev[prev.length - 1], curr]]
      : [...prev, [curr]],
  []
);
//=> [
//   [0, 1, 2, 3, 4, 5, 6, 7],
//   [8, 9, 10, 11, 12, 13, 14, 15],
//   [16, 17, 18, 19, 20, 21, 22, 23],
//   [24, 25, 26, 27, 28, 29, 30, 31],
//   [32, 33, 34, 35, 36, 37, 38, 39],
//   [40, 41, 42, 43, 44, 45, 46, 47],
//   [48, 49, 50, 51, 52, 53, 54, 55],
//   [56, 57, 58, 59, 60, 61, 62, 63],
//   [64, 65, 66, 67, 68, 69, 70, 71],
//   [72, 73, 74, 75, 76, 77, 78, 79],
//   [80, 81, 82, 83, 84, 85, 86, 87],
//   [88, 89, 90, 91, 92, 93, 94, 95],
//   [96, 97, 98, 99]
// ];

lodash使える環境

const arr = [...Array(100).keys()];
const size = 8
const result = _(arr).chunk(size).value()