How to split and array into n arrays javascript

July 5, 2022

let’s say i have an array [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] and i want to split it into n parts let’s say 3 part so the result is supposed to be [ 1, 2, 3, 4 ],[ 4, 5, 6, 7],[ 8, 9, 10 ] but the code i have right now is or O(n*m) which is bad. Is there an optimal way of doing this?

const items = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

const n = 3
const result = [[], [], []]

const wordsPerLine = Math.ceil(items.length / 3)

for (let line = 0; line < n; line++) {
  for (let i = 0; i < wordsPerLine; i++) {
     const value = items[i + line * wordsPerLine]
      if (!value) continue //avoid adding "undefined" values
      result[line].push(value)
  }
}

>Solution :

To split up the array as evenly as possible:

function split_array(a, nparts) {
  const quot = Math.floor(a.length / nparts)
  const rem = a.length % nparts
  var parts = []
  for (var i = 0; i < nparts; ++i) {
    parts.push(a.splice(0, quot + (i < rem)))
  }
  return parts
}

var chunks = split_array([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 3)
console.log(JSON.stringify(chunks))

Output: