js将数组分为多个数组（指定几个）

function splitUp(arr, n) {
  var rest = arr.length % n, // how much to divide
    restUsed = rest, // to keep track of the division over the elements
    partLength = Math.floor(arr.length / n),
    result = [];
  for (var i = 0; i < arr.length; i += partLength) {
    var end = partLength + i,
      add = false;
    if (rest !== 0 && restUsed) { // should add one element for the division
      end++;
      restUsed--; // we've used one division element now
      add = true;
    }
    result.push(arr.slice(i, end)); // part of the array
    if (add) {
      i++; // also increment i in the case we added an extra element for division
    }
  }
  return result;
}