Learn Functional Programming by Building a Spreadsheet - Step 35

Tell us what’s happening:

fCC test constantly states: " Your rangeRegex should use a character class in the capture group. Your rangeRegex should use a character class to match A through J."

Can someone please fully explain, where I have NOT used a character class in the capture group.
As the fCC tests are Very verbose; the instructions should Explicitly state what character class and capture group are required; as there are many different acceptable solutions; yet the fCC test is only concerned with ONE specific solution!
I have tried different regex variations in my local environment and they work.
This type of response from the fCC tests is NOT HELPFUL to those new to learning javascript.



https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures-v8/learn-functional-programming-by-building-a-spreadsheet/step-35

Your code so far

<!-- file: index.html -->
<!DOCTYPE html>
<html lang="en">
  <head>
    <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>
  </head>
  <body>
    <div id="container">
      <div></div>
    </div>
    <script src="./script.js"></script>
  </body>
</html>
/* 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;

const median = nums => {
  const sorted = nums.slice().sort((a, b) => a - b);
  const length = sorted.length;
  const middle = length / 2 - 1;
  return isEven(length)
    ? average([sorted[middle], sorted[middle + 1]])
    : sorted[Math.ceil(middle)];
}

const spreadsheetFunctions = {
  sum,
  average,
  median
}

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));


// User Editable Region

const evalFormula = (x, cells) => {
  const idToText = id => cells.find(cell => cell.id === id).value;
  const rangeRegex = /([A-J][1-9])\d*:([A-J][1-9])\d*|([A-J][1-9]\d*)/g;
}

// User Editable Region


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

const update = event => {
  const element = event.target;
  const value = element.value.replace(/\s/g, "");
  if (!value.includes(element.id) && value.startsWith('=')) {

  }
}

Your browser information:

User Agent is: Mozilla/5.0 (X11; Linux x86_64; rv:122.0) Gecko/20100101 Firefox/122.0

Challenge Information:

Learn Functional Programming by Building a Spreadsheet - Step 35

Composing the full regex is split in few steps here. In this step literally is expected to be able to match the first character of range.