A minuscule reusable lib in JS to begin working with collections

utils.js

const mult = (...args) => args.reduce((t, c) => t * c);

const array = (size, value) => new Array(size).fill(value);

const zeros = size => array(size, 0);

const partition = (size, coll) => {
  if (size === undefined && coll === undefined) {
    return partition;
  }

  if (coll === undefined) {
    return coll2 => partition(size, coll2);
  }

  if (size <= 0) {
    return coll;
  }

  const result = [];
  const length = coll.length;

  for (let i = 0; i < length; i += size) {
    result.push(coll.slice(i, i + size));
  }

  return result;
};

const split = (size, coll) => {
  const items = coll.length / size;
  const result = [];

  for (let i = 0; i < coll.length; i += items) {
    result.push(coll.slice(i, i + items));
  }

  return result;
};

const reshape = (dims, coll) => {
  if (dims === undefined && coll === undefined) {
    throw new Error("z");
  }

  if (coll.length !== mult(...dims)) {
    throw new Error("z");
  }

  if (coll === undefined) {
    return coll2 => reshape(dims, coll2);
  }

  if (dims.length <= 1) {
    return coll;
  }

  const [first, ...rest] = dims;

  return split(first, coll).map(c => reshape(rest, c));
};