--- id: 646d3e64b15f92be6e61704e title: Step 70 challengeType: 0 dashedName: step-70 --- # --description-- The `regex` you will be passing to your `infixEval` function will match two numbers with an operator between them. The first number will be assigned to `arg1` in the callback, the second to `arg2`, and the operator to `operator`. Have your callback function implicitly return the `operator` property of your `infixToFunction` object. Remember that `operator` is a variable which holds the property name, not the actual property name. # --hints-- Your callback should use an implicit return. ```js assert.notMatch(code, /const\s+infixEval\s*=\s*\(\s*str\s*,\s*regex\s*\)\s*=>\s*str\.replace\(\s*regex\s*,\s*\(\s*_match\s*,\s*arg1\s*,\s*operator\s*,\s*arg2\s*\)\s*=>\s*\{/); ``` Your callback function should access the `infixToFunction` object. ```js assert.match(code, /const\s+infixEval\s*=\s*\(\s*str\s*,\s*regex\s*\)\s*=>\s*str\.replace\(\s*regex\s*,\s*\(\s*_match\s*,\s*arg1\s*,\s*operator\s*,\s*arg2\s*\)\s*=>\s*infixToFunction/); ``` Your callback function should use bracket notation to access the property of the `infixToFunction` object that matches the value of the `operator` parameter. ```js assert.match(code, /const\s+infixEval\s*=\s*\(\s*str\s*,\s*regex\s*\)\s*=>\s*str\.replace\(\s*regex\s*,\s*\(\s*_match\s*,\s*arg1\s*,\s*operator\s*,\s*arg2\s*\)\s*=>\s*infixToFunction\s*\[\s*operator\s*\]\s*\)/); ``` # --seed-- ## --seed-contents-- ```html Functional Programming Spreadsheet
``` ```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; } ``` ```js const infixToFunction = { "+": (x, y) => x + y, "-": (x, y) => x - y, "*": (x, y) => x * y, "/": (x, y) => x / y, } --fcc-editable-region-- const infixEval = (str, regex) => str.replace(regex, (_match, arg1, operator, arg2) => {}); --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('=')) { } } ```