const string = "A".repeat(8000)

//methode 1
function chunkString(str, length) {
  return str.match(new RegExp('.{1,' + length + '}', 'g'));
}
//methode 2
function chunkSubstr(str, size) {
  const numChunks = Math.ceil(str.length / size)
  const chunks = new Array(numChunks)

  for (let i = 0, o = 0; i < numChunks; ++i, o += size) {
    chunks[i] = str.substr(o, size)
  }

  return chunks
}

console.log(chunkSubstr(string, 4096))