Learn Functional Programming by Building a Spreadsheet - Step 22

Tell us what’s happening:

I’m not sure if I’m just being dumb or anything but I’m having a hard time understanding these specific instructions: “sorting a copy of the nums array.” I don’t know how exactly to sort it in the way it’s telling me to.

Your code so far

<!-- file: index.html -->
<!DOCTYPE html>
<html lang="en">
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link rel="stylesheet" href="./styles.css" />
    <title>Functional Programming Spreadsheet</title>
    <div id="container">
    <script src="./script.js"></script>
/* file: styles.css */
#container {
  display: grid;
  grid-template-columns: 50px repeat(10, 200px);
  grid-template-rows: repeat(11, 30px);

.label {
  background-color: lightgray;
  text-align: center;
  vertical-align: middle;
  line-height: 30px;
/* file: script.js */
const isEven = num => num % 2 === 0;
const sum = nums => nums.reduce((acc, el) => acc + el, 0);
const average = nums => sum(nums) / nums.length;

// User Editable Region

const median = (nums) => {
  const sorted = nums.slice().sort(() => );

// User Editable Region

const range = (start, end) => Array(end - start + 1).fill(start).map((element, index) => element + index);
const charRange = (start, end) => range(start.charCodeAt(0), end.charCodeAt(0)).map(code => String.fromCharCode(code));

window.onload = () => {
  const container = document.getElementById("container");
  const createLabel = (name) => {
    const label = document.createElement("div");
    label.className = "label";
    label.textContent = name;
  const letters = charRange("A", "J");
  range(1, 99).forEach(number => {
    letters.forEach(letter => {
      const input = document.createElement("input");
      input.type = "text";
      input.id = letter + number;
      input.ariaLabel = letter + number;

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/ Safari/537.36 OPR/

Challenge Information:

Learn Functional Programming by Building a Spreadsheet - Step 22

Hi there. The sort method needs to receive a callback function with two variables. Like other callback functions made so far , two parameters are defined in parentheses and an operation is performed with these two parameters to determine the order.

Traditionally these two variables are called a and b because they represent the first and second number. The first element is deemed smaller by returning a negative number; the first element is deemed bigger by returning a positive number. If it returns zero, then the two are equal.

Hope this helps. :slight_smile:

P.S More on the sort callback.

Hi, although I have not came to your level, I would like to say something about my understanding, for “sorting a copy of the nums array.”, is the meaning that using a copy of array? if so, I think it should be using like this […nums].

The word “sorting” is where I’m confused at. I already know how to make a copy of an array and that’s by using the slice() method.

While I didn’t read the whole thing (sorry), your reply DID remind me of the “minus” technique. So I’ll consider your reply as the solution. Thanks! :grinning:

The course has been updated and Step 22 is now the “average the nums array” step.