curriculum/challenges/english/blocks/learn-functional-programming-by-building-a-spreadsheet/646d3c146e10b0ba222bb2a7.md
In mathematics, an <dfn>infix</dfn> is a mathematical operator that appears between its two operands. For example, 1 + 2 is an infix expression.
To parse these expressions, you will need to map the symbols to relevant functions. Declare an infixToFunction variable, and assign it an empty object.
You should declare an infixToFunction variable.
assert.match(code, /(?:const|let|var)\s+infixToFunction/);
You should use const to declare your infixToFunction variable.
assert.match(code, /const\s+infixToFunction/);
Your infixToFunction variable should be an object.
assert.isObject(infixToFunction);
Your infixToFunction object should be empty.
assert.lengthOf(Object.keys(infixToFunction), 0);
<!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>
#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;
}
--fcc-editable-region--
--fcc-editable-region--
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));
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()));
}
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('=')) {
}
}