# Learn Functional Programming by Building a Spreadsheet - Step 99

### Tell us what’s happening:

I tried to best I could, but I’m stuck. The syntax for the has2 is kind of confusing.

``````<!-- file: index.html -->
<!DOCTYPE html>
<html lang="en">
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<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 infixToFunction = {
"+": (x, y) => x + y,
"-": (x, y) => x - y,
"*": (x, y) => x * y,
"/": (x, y) => x / y,
}

const infixEval = (str, regex) => str.replace(regex, (_match, arg1, operator, arg2) => infixToFunction[operator](parseFloat(arg1), parseFloat(arg2)));

const highPrecedence = str => {
const regex = /([\d.]+)([*\/])([\d.]+)/;
const str2 = infixEval(str, regex);
return str === str2 ? str : highPrecedence(str2);
}

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)];
}

// User Editable Region

sum,
average,
median,
even: nums => nums.filter(isEven),
firsttwo: nums => nums.slice(0, 2),
lasttwo: nums => nums.slice(-2),
has2: nums => nums.contains(2),
increment: nums
}

// User Editable Region

const applyFunction = str => {
const noHigh = highPrecedence(str);
const infix = /([\d.]+)([+-])([\d.]+)/;
const str2 = infixEval(noHigh, infix);
const functionCall = /([a-z0-9]*)\(([0-9., ]*)\)(?!.*\()/i;
const toNumberList = args => args.split(",").map(parseFloat);
const apply = (fn, args) => spreadsheetFunctions[fn.toLowerCase()](toNumberList(args));
return str2.replace(functionCall, (match, fn, args) => spreadsheetFunctions.hasOwnProperty(fn.toLowerCase()) ? apply(fn, args) : match);
}

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));

const evalFormula = (x, cells) => {
const idToText = id => cells.find(cell => cell.id === id).value;
const rangeRegex = /([A-J])([1-9][0-9]?):([A-J])([1-9][0-9]?)/gi;
const rangeFromString = (num1, num2) => range(parseInt(num1), parseInt(num2));
const elemValue = num => character => idToText(character + num);
const addCharacters = character1 => character2 => num => charRange(character1, character2).map(elemValue(num));
const rangeExpanded = x.replace(rangeRegex, (_match, char1, num1, char2, num2) => rangeFromString(num1, num2).map(addCharacters(char1)(char2)));
const cellRegex = /[A-J][1-9][0-9]?/gi;
const cellExpanded = rangeExpanded.replace(cellRegex, match => idToText(match.toUpperCase()));
const functionExpanded = applyFunction(cellExpanded);
return functionExpanded === x ? functionExpanded : evalFormula(functionExpanded, cells);
}

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('=')) {
element.value = evalFormula(value.slice(1), Array.from(document.getElementById("container").children));
}
}
``````

User Agent is: `Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36`

### Challenge Information:

Learn Functional Programming by Building a Spreadsheet - Step 99

I think I got has2, but the increment is what I’m having trouble with.

I am having the same issue on this as well.
Your `has2` looks a bit off as `contains` is not a method as far as I can tell.
`increment`, i tried `nums => Array(nums.forEach(num => num + 1))` but that isn’t working for me.

I know, I changed ‘contains’ to ‘includes.’ I shall try increment once more. If I’m still struggling, then I’ll let you know.

1 Like

Try with `.map`, as it returns a new array.
`.forEach` always returns undefined. This is where I went wrong

Source:
.forEach: Array.prototype.forEach() - JavaScript | MDN
.map: Array.prototype.map() - JavaScript | MDN

Here’s the feedback I’m getting: “Your has2 function should return true if the array has 2 in it.” I’d like to know the error based on the feedback.

Hey Kodu,

What is your code looking like now?

Here it is:

``````const spreadsheetFunctions = {
sum,
average,
median,
even: nums => nums.filter(isEven),
firsttwo: nums => nums.slice(0, 2),
lasttwo: nums => nums.slice(-2),
has2: nums => nums.map(2) ? true : false,
increment: i => nums[i]++
}
``````

Hey Kodu,

For `has2`: We don’t need to use the `.map()` function because we don’t need to return an array. Based off your previous comments, you had it right to be `nums.includes(arg)`. This will check the array and return true if `arg` is found in the array, otherwise false.

For `increment`: Your arrow function is a bit off. I see that you are wanting to increment each value in the array, however this would throw a syntax error as `nums` is not defined to this particular function. `nums` is a parameter for some of the previous functions, but they are local. We would want to use a `.map()` method for incrementing each index of an array because `.map()` would allow us to iterate through an array and return a new one based on the callback function provided as a parameter.

Something like this: `array.map(index => index + 1)`source
Of course, replacing with the right names!

Happy coding (: