zip.js

//#   zip :: Array a -> Array a -> Array a
//.
//.   Zip two arrays, xs and ys, of arbitrary lengths.
//.
//.   let n = Math.min (xs.length, ys.length);
//.
//.   If the first array is longer than the second, the result will
//.   consist of the first n + 1 elements of the first array and
//.   all n elements of the second array. Otherwise, the result will
//.   consist of the first n elements of each array.
//.
//.   > zip ([1, 3, 5]) ([2])
//.   [1, 2, 3]
//.
//.   > zip ([1, 3, 5]) ([2, 4])
//.   [1, 2, 3, 4, 5]
//.
//.   > zip ([1, 3, 5]) ([2, 4, 6])
//.   [1, 2, 3, 4, 5, 6]
//.
//.   > zip ([1, 3, 5]) ([2, 4, 6, 8])
//.   [1, 2, 3, 4, 5, 6]
const zip = xs => ys => {
  const result = [];
  for (let idx = 0; idx < xs.length; idx += 1) {
    result.push (xs[idx]);
    if (idx === ys.length) break;
    result.push (ys[idx]);
  }
  return result;
};