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Complete solutions for callbacks #20

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302 changes: 302 additions & 0 deletions callbacks.js
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Original file line number Diff line number Diff line change
Expand Up @@ -130,3 +130,305 @@ function objectFilter(obj, callback) {
// Paris: 'PARIS',
// };
// console.log(objectFilter(cities, city => city.toUpperCase())) // Should log { London: 'LONDON', Paris: 'PARIS'}


//Extension 8
function majority(array, callback) {
let countT = 0;
let countF = 0;
for (let i = 0; i < array.length; i++) {
callback(array[i]) ? ++countT : ++countF;
}

return countT > countF;
}

// /*** Uncomment these to check your work! ***/
// const isOdd2 = function(num) { return num % 2 === 1; };
// console.log(majority([1, 2, 3, 4, 5], isOdd2)); // should log: true
// console.log(majority([2, 3, 4, 5], isOdd2)); // should log: false

//Extension 9
function prioritize(array, callback) {
const res = [];
for (let i = 0; i < array.length; i++) {
if (callback(array[i])) {
res.push(array[i]);
}
}
for (let i = 0; i < array.length; i++) {
if (!callback(array[i])) {
res.push(array[i]);
}
}
return res;
}

// /*** Uncomment these to check your work! ***/
// const startsWithS = function(str) { return str[0] === 's' || str[0] === 'S'; };
// console.log(prioritize(['curb', 'rickandmorty', 'seinfeld', 'sunny', 'friends'], startsWithS));
// should log: ['seinfeld', 'sunny', 'curb', 'rickandmorty', 'friends']

//Extension 10
function countBy(array, callback) {
const res = {};
let countO = 0,
countE = 0;
for (let num of array) {
let key = callback(num);
key === "odd" ? (res[key] = ++countO) : (res[key] = ++countE);
}
return res;
}

// /*** Uncomment these to check your work! ***/
// console.log(countBy([1, 2, 3, 4, 5], function(num) {
// if (num % 2 === 0) return 'even';
// else return 'odd';
// }));
// should log: { odd: 3, even: 2 }

//Extension 11
function groupBy(array, callback) {
const res = {};
for (let i of array) {
let dec = callback(i);
if (dec in res) {
res[dec].push(i);
} else {
res[dec] = [i];
}
}
return res;
}

//using reduce
function groupBy(array, callback) {
return array.reduce((res, i) => {
const dec = callback(i);
if (dec in res) {
res[dec].push(i);
} else {
res[dec] = [i];
}
return res;
}, {});
}

// /*** Uncomment these to check your work! ***/
// const decimals = [1.3, 2.1, 2.4];
// const floored = function(num) { return Math.floor(num); };
// console.log(groupBy(decimals, floored));
// should log: { 1: [1.3], 2: [2.1, 2.4] }

//Extension 12
function goodKeys(obj, callback) {
const res = [];
for (let key in obj) {
if (callback(obj[key])) {
res.push(key);
}
}
return res;
}

// /*** Uncomment these to check your work! ***/
// const sunny = { mac: 'priest', dennis: 'calculating', charlie: 'birdlaw', dee: 'bird', frank: 'warthog' };
// const startsWithBird = function(str) { return str.slice(0, 4).toLowerCase() === 'bird'; };
// console.log(goodKeys(sunny, startsWithBird)); // should log: ['charlie', 'dee']

//Extension 13
function commutative(func1, func2, value) {
let op = func2(func1(value));
let op2 = func1(func2(value));

return op === op2;
}

// /*** Uncomment these to check your work! ***/
// const multBy3 = (n) => n * 3;
// const divBy4 = (n) => n / 4;
// const subtract5 = (n) => n - 5;
// console.log(commutative(multBy3, divBy4, 11)); // should log: true
// console.log(commutative(multBy3, subtract5, 10)); // should log: false
// console.log(commutative(divBy4, subtract5, 48)); // should log: false

//Extension 14
function objFilter(obj, callback) {
const res = {};

for (let key in obj) {
if (obj[key] === callback(key)) {
res[key] = obj[key];
}
}
return res;
}

// /*** Uncomment these to check your work! ***/
// const startingObj = {};
// startingObj[6] = 3;
// startingObj[2] = 1;
// startingObj[12] = 4;
// const half = (n) => n / 2;
// console.log(objFilter(startingObj, half)); // should log: { 2: 1, 6: 3 }

//Extension 15
function rating(arrOfFuncs, value) {
let count = 0;
for (let func of arrOfFuncs) {
if (func(value)) {
count++;
}
}

return (count / arrOfFuncs.length) * 100;
}

// Using filter

function rating(arrOfFuncs, value) {
if (arrOfFuncs.length === 0) return 0;
const count = arrOfFuncs.filter((func) => func(value)).length;
return (count / arrOfFuncs.length) * 100;
}
// /*** Uncomment these to check your work! ***/
// const isEven = (n) => n % 2 === 0;
// const greaterThanFour = (n) => n > 4;
// const isSquare = (n) => Math.sqrt(n) % 1 === 0;
// const hasSix = (n) => n.toString().includes("6");
// const checks = [isEven, greaterThanFour, isSquare, hasSix];
// console.log(rating(checks, 64)); // should log: 100
// console.log(rating(checks, 66)); // should log: 75

//Extension 16
function pipe(arrOfFuncs, value) {
let result = value;
for (let func of arrOfFuncs) {
result = func(result);
}
return result;
}

//Using reduce

function pipe(arrOfFuncs, value) {
return arrOfFuncs.reduce((acc, func) => func(acc), value);
}

// /*** Uncomment these to check your work! ***/
// const capitalize = (str) => str.toUpperCase();
// const addLowerCase = (str) => str + str.toLowerCase();
// const repeat = (str) => str + str;
// const capAddlowRepeat = [capitalize, addLowerCase, repeat];
// console.log(pipe(capAddlowRepeat, "cat")); // should log: 'CATcatCATcat'

//Extension 17
function highestFunc(objOfFuncs, subject) {
let highestKey = null;
let highestResult = -Infinity;

for (let key of Object.keys(objOfFuncs)) {
let result = objOfFuncs[key](subject);

if (result > highestResult) {
highestKey = key;
highestResult = result;
}
}
return highestKey;
}

// Using Object.entries

function highestFunc(objOfFuncs, subject) {
let highestKey = null;
let highestResult = -Infinity;

//Iterate over keys and values in a single loop instead of writing `Object.keys` and getting its value from key
for (const [key, func] of Object.entries(objOfFuncs)) {
let result = func(subject);

if (result > highestResult) {
highestKey = key;
highestResult = result;
}
}
return highestKey;
} // /*** Uncomment these to check your work! ***/
// const groupOfFuncs = {};
// groupOfFuncs.double = (n) => n * 2;
// groupOfFuncs.addTen = (n) => n + 10;
// groupOfFuncs.inverse = (n) => n * -1;
// console.log(highestFunc(groupOfFuncs, 5)); // should log: 'addTen'
// console.log(highestFunc(groupOfFuncs, 11)); // should log: 'double'
// console.log(highestFunc(groupOfFuncs, -20)); // should log: 'inverse'

//Extension 18
function combineOperations(startVal, arrOfFuncs) {
// let result = startVal;
// for(let func of arrOfFuncs){
// result = func(result);
// }
// return result;

//using reduce

// return arrOfFuncs.reduce((acc,func)=>func(acc),startVal)

//utilising the previously written func
return pipe(arrOfFuncs, startVal);
}

function add100(num) {
return num + 100;
}

function divByFive(num) {
return num / 5;
}

function multiplyByThree(num) {
return num * 3;
}

// /*** Uncomment these to check your work! ***/
// console.log(combineOperations(0, [add100, divByFive, multiplyByThree])); // Should output 60 -->
// console.log(combineOperations(0, [divByFive, multiplyByThree, add100])); // Should output 100

//Extension 19
function myFunc(array, callback) {
for (let i = 0; i < array.length; i++) {
if (callback(array[i])) return 1;
}
return -1;
}

const numbers = [2, 3, 6, 64, 10, 8, 12];
const evens = [2, 4, 6, 8, 10, 12, 64];

function isOdd(num) {
return num % 2 !== 0;
}

// /*** Uncomment these to check your work! ***/
// console.log(myFunc(numbers, isOdd)); // Output should be 1
// console.log(myFunc(evens, isOdd)); // Output should be -1

//Extension 20
function myForEach(array, callback) {
for (let i = 0; i < array.length; i++) {
callback(array[i]);
}
}

let sum = 0;

function addToSum(num) {
sum += num;
}

// /*** Uncomment these to check your work! ***/
// const nums2 = [1, 2, 3];
// myForEach(nums2, addToSum);
// console.log(sum); // Should output 6