js实现 chunk 函数分组数组

// 自己实现
function chunk(list, size) {
    let len = list.length;
    if (size < 1 || !len) {
        return [];
    }
    if (size > len) {
        return [list];
    }
    // 最终返回数组
    let res = [];
    // 向下取整
    let integer = Math.floor(len / size);
    // 取余
    let rest = len % size;
    for (let i = 1; i <= integer; i++) {
        res.push(list.splice(0, size));
    }
    if (rest) {
        res.push(list.splice(0, rest));
    }
    return res;
}
// console.log(chunk([1, 2, 3, 4, 5], 0));
console.log(chunk([1, 2, 3, 4, 5], -1));
console.log(chunk([1, 2, 3, 4, 5], 2));
console.log(chunk([1, 2, 3, 4, 5], 3));
console.log(chunk([1, 2, 3, 4, 5], 4));
console.log(chunk([1, 2, 3, 4, 5], 5));
console.log(chunk([1, 2, 3, 4, 5], 6));
// []
// []
// [ [ 1, 2 ], [ 3, 4 ], [ 5 ] ]
// [ [ 1, 2, 3 ], [ 4, 5 ] ]
// [ [ 1, 2, 3, 4 ], [ 5 ] ]
// [ [ 1, 2, 3, 4, 5 ] ]
// [ [ 1, 2, 3, 4, 5 ] ]

网上找到的lodash源码（供参考）：

function chunk(array, size) {
  size = Math.max(size, 0)
  const length = array == null ? 0 : array.length
  if (!length || size < 1) {
    return []
  }
  let index = 0
  let resIndex = 0
  const result = new Array(Math.ceil(length / size))

  while (index < length) {
    result[resIndex++] = slice(array, index, (index += size))
  }
  return result
}