--- id: 646d0db5175974ad8633b71c title: Step 47 challengeType: 0 dashedName: step-47 --- # --description-- Your inner functions can also return a function. Using the same arrow syntax, update your `addCharacters` function to return a third function which takes a `num` parameter. # --hints-- Your inner arrow function should return another arrow function with a `num` parameter. ```js assert.match(code, /const\s+evalFormula\s*=\s*\(\s*x\s*,\s*cells\s*\)\s*=>\s*{\s*const\s+idToText\s*=\s*(\(\s*id\s*\)|id)\s*=>\s*cells\.find\(\s*(\(\s*cell\s*\)|cell)\s*=>\s*(?:cell\.id\s*===\s*id|id\s*===\s*cell\.id)\s*\)\.value\s*;?\s*const\s+rangeRegex\s*=\s*\/\(\[A-J\]\)\(\[1-9\]\[0-9\]\?\):\(\[A-J\]\)\(\[1-9\]\[0-9\]\?\)\/(gi|ig)\s*;?\s*const\s+rangeFromString\s*=\s*\(\s*num1\s*,\s*num2\s*\)\s*=>\s*range\(\s*parseInt\(\s*num1\s*\)\s*,\s*parseInt\(\s*num2\s*\)\s*\)\s*;?\s*const\s+elemValue\s*=\s*(\(\s*num\s*\)|num)\s*=>\s*\{\s*const\s+inner\s*=\s*(\(\s*character\s*\)|character)\s*=>\s*\{\s*return\s+idToText\(\s*character\s*\+\s*num\s*\)\s*;?\s*}\s*;?\s*return\s+inner\s*;?\s*\}\s*const\s+addCharacters\s*=\s*(\(\s*character1\s*\)|character1)\s*=>\s*(\(\s*character2\s*\)|character2)\s*=>\s*(\(\s*num\s*\)|num)\s*=>/); ``` Your inner-most arrow function should be empty. ```js assert.match(code, /const\s+evalFormula\s*=\s*\(\s*x\s*,\s*cells\s*\)\s*=>\s*{\s*const\s+idToText\s*=\s*(\(\s*id\s*\)|id)\s*=>\s*cells\.find\(\s*(\(\s*cell\s*\)|cell)\s*=>\s*(?:cell\.id\s*===\s*id|id\s*===\s*cell\.id)\s*\)\.value\s*;?\s*const\s+rangeRegex\s*=\s*\/\(\[A-J\]\)\(\[1-9\]\[0-9\]\?\):\(\[A-J\]\)\(\[1-9\]\[0-9\]\?\)\/(gi|ig)\s*;?\s*const\s+rangeFromString\s*=\s*\(\s*num1\s*,\s*num2\s*\)\s*=>\s*range\(\s*parseInt\(\s*num1\s*\)\s*,\s*parseInt\(\s*num2\s*\)\s*\)\s*;?\s*const\s+elemValue\s*=\s*(\(\s*num\s*\)|num)\s*=>\s*\{\s*const\s+inner\s*=\s*(\(\s*character\s*\)|character)\s*=>\s*\{\s*return\s+idToText\(\s*character\s*\+\s*num\s*\)\s*;?\s*}\s*;?\s*return\s+inner\s*;?\s*\}\s*const\s+addCharacters\s*=\s*(\(\s*character1\s*\)|character1)\s*=>\s*(\(\s*character2\s*\)|character2)\s*=>\s*(\(\s*num\s*\)|num)\s*=>\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 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)); --fcc-editable-region-- 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 => { const inner = character => { return idToText(character + num); } return inner; } const addCharacters = character1 => character2 => { } } --fcc-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('=')) { } } ```