---
id: 646d4b3d80ea98d824c8a4f9
title: Step 105
challengeType: 0
dashedName: step-105
---
# --description--
Finally, to handle potential edge cases, add an empty string property (you will need to use quotes) which is a function that takes a single argument and returns that argument.
With that, your spreadsheet project is now complete. You are welcome to experiment with adding support for even more functions.
# --hints--
Your `spreadsheetFunctions` object should have an empty string property.
```js
assert.property(spreadsheetFunctions, "");
```
Your empty string property should be a function.
```js
assert.isFunction(spreadsheetFunctions[""]);
```
Your empty string property function should return the argument.
```js
assert.deepEqual(spreadsheetFunctions[""]([1,2,3]), [1,2,3]);
```
# --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,
}
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)];
}
--fcc-editable-region--
const spreadsheetFunctions = {
sum,
average,
median,
even: nums => nums.filter(isEven),
someeven: nums => nums.some(isEven),
everyeven: nums => nums.every(isEven),
firsttwo: nums => nums.slice(0, 2),
lasttwo: nums => nums.slice(-2),
has2: nums => nums.includes(2),
increment: nums => nums.map(num => num + 1),
random: ([x, y]) => Math.floor(Math.random() * y + x),
range: nums => range(...nums),
nodupes: nums => [...new Set(nums).values()]
}
--fcc-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);
}
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('=')) {
element.value = evalFormula(value.slice(1), Array.from(document.getElementById("container").children));
}
}
```
# --solutions--
```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,
}
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)];
}
const spreadsheetFunctions = {
"": x => x,
sum,
average,
median,
even: nums => nums.filter(isEven),
someeven: nums => nums.some(isEven),
everyeven: nums => nums.every(isEven),
firsttwo: nums => nums.slice(0, 2),
lasttwo: nums => nums.slice(-2),
has2: nums => nums.includes(2),
increment: nums => nums.map(num => num + 1),
random: ([x, y]) => Math.floor(Math.random() * y + x),
range: nums => range(...nums),
nodupes: nums => [...new Set(nums).values()]
}
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);
}
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('=')) {
element.value = evalFormula(value.slice(1), Array.from(document.getElementById("container").children));
}
}
```