@@ -0,0 +1,7 @@
+function addTwo(num) {
+return num + 2;
+}
+
+// To check if you've completed it, uncomment these console.logs!
+// console.log(addTwo(3));
+// console.log(addTwo(10));

@@ -0,0 +1,7 @@
+function addS(word) {
+return word + 's';
+}
+
+// uncomment these to check your work
+// console.log(addS('pizza'));
+// console.log(addS('bagel'));

@@ -0,0 +1,9 @@
+function map(array, callback) {
+const result = [];
+for (const el of array) {
+result.push(callback(el));
+}
+return result;
+}
+
+// console.log(map([1, 2, 3], addTwo));

@@ -0,0 +1,7 @@
+function forEach(array, callback) {
+for (let i = 0; i < array.length; i++) {
+callback(array[i], i, array);
+}
+}
+
+// forEach([1, 2, 3], (el) => console.log(el))

@@ -0,0 +1,7 @@
+function mapWith(array, callback) {
+const result = [];
+array.forEach(el => result.push(callback(el)));
+return result;
+}
+
+// console.log(mapWith([1, 2, 3], addTwo));

@@ -0,0 +1,9 @@
+function reduce(array, callback, initialValue) {
+for (let i = 0; i < array.length; i++) {
+initialValue = callback(initialValue, array[i]);
+}
+return initialValue;
+}
+
+const add = (acc, el) => acc + el;
+console.log(reduce([1, 2, 3], add, 0));

@@ -0,0 +1,10 @@
+function union(...arrays) {
+return arrays.reduce((acc, arr) => {
+arr.forEach(el => {
+if (!acc.includes(el)) {
+acc.push(el);
+}
+});
+return acc;
+})
+}

@@ -0,0 +1,10 @@
+function objOfMatches(array1, array2, callback) {
+return array1.reduce((res, el, i) => {
+if (callback(el) === array2[i]) {
+res[el] = array2[i];
+}
+return res;
+}, {})
+}
+
+console.log(objOfMatches(['hi', 'howdy', 'bye', 'later', 'hello'], ['HI', 'Howdy', 'BYE', 'LATER', 'hello'], function(str) { return str.toUpperCase(); })); // should log: { hi: 'HI', bye: 'BYE', later: 'LATER' }

@@ -0,0 +1,9 @@
+function multiMap(arrVals, arrCallbacks) {
+return arrVals.reduce((res, key) => {
+res[key] = arrCallbacks.map(callback => callback(key))
+return res;
+}, {})
+}
+
+console.log(multiMap(['catfood', 'glue', 'beer'], [function(str) { return str.toUpperCase(); }, function(str) { return str[0].toUpperCase() + str.slice(1).toLowerCase(); }, function(str) { return str + str; }]));
+// should log: { catfood: ['CATFOOD', 'Catfood', 'catfoodcatfood'], glue: ['GLUE', 'Glue', 'glueglue'], beer: ['BEER', 'Beer', 'beerbeer'] }

@@ -0,0 +1,15 @@
+function objectFilter(obj, callback) {
+return Object.keys(obj).reduce((res, key) => {
+if (obj[key] === callback(key)) {
+res[key] = obj[key];
+}
+return res;
+}, {})
+}
+
+const cities = {
+London: 'LONDON',
+LA: 'Los Angeles',
+Paris: 'PARIS',
+};
+console.log(objectFilter(cities, city => city.toUpperCase())) // Should log { London: 'LONDON', Paris: 'PARIS'}

@@ -0,0 +1,18 @@
+function majority(array, callback) {
+count = {
+true: 0,
+false: 0
+}
+
+array.forEach(el => count[callback(el)]++)
+
+if (count[true] > count[false]) {
+return true;
+} else {
+return false;
+}
+}
+
+const isOdd = function(num) { return num % 2 === 1; };
+console.log(majority([1, 2, 3, 4, 5], isOdd)); // should log: true
+console.log(majority([2, 3, 4, 5], isOdd)); // should log: false

@@ -0,0 +1,14 @@
+function prioritize(array, callback) {
+const res = {
+true: [],
+false: []
+}
+
+array.forEach(el => res[callback(el)].push(el));
+return res[true].concat(res[false]);
+}
+
+// /*** 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']

@@ -0,0 +1,13 @@
+function countBy(array, callback) {
+return array.reduce((res, el) => {
+const key = callback(el);
+res[key] = res[key] !== undefined ? ++res[key] : 1;
+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 }

@@ -0,0 +1,15 @@
+function groupBy(array, callback) {
+return array.reduce((res, el) => {
+const key = callback(el);
+if (res[key] !== undefined) {
+res[key].push(el);
+} else {
+res[key] = [el];
+};
+return res;
+}, {})
+}
+
+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] }

@@ -0,0 +1,7 @@
+function goodKeys(obj, callback) {
+return Object.keys(obj).filter(key => callback(obj[key]));
+}
+
+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']

@@ -0,0 +1,13 @@
+function commutative(func1, func2, value) {
+const firstRes = func1(func2(value));
+const secondRes = func2(func1(value));
+return firstRes === secondRes;
+}
+
+// /*** 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

@@ -0,0 +1,15 @@
+function objFilter(obj, callback) {
+return Object.keys(obj).reduce((res, key) => {
+if (callback(key) === obj[key]) {
+res[key] = obj[key];
+}
+return res;
+}, {});
+}
+
+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 }

@@ -0,0 +1,13 @@
+function rating(arrOfFuncs, value) {
+const trueArr = arrOfFuncs.filter(func => func(value));
+const percentage = (trueArr.length / arrOfFuncs.length) * 100;
+return percentage;
+}
+
+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

@@ -0,0 +1,9 @@
+function pipe(arrOfFuncs, value) {
+return arrOfFuncs.reduce((acc, func) => func(acc), value);
+}
+
+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'

@@ -0,0 +1,20 @@
+function highestFunc(objOfFuncs, subject) {
+const keys = Object.keys(objOfFuncs);
+return keys.reduce((prevKey, key) => {
+const prevFuncRes = objOfFuncs[prevKey](subject);
+const curFuncRes = objOfFuncs[key](subject);
+if (curFuncRes > prevFuncRes) {
+return key;
+} else {
+return prevKey;
+}
+}, keys[0])
+}
+
+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'

@@ -0,0 +1,26 @@
+function combineOperations(startVal, arrOfFuncs) {
+return arrOfFuncs.reduce((acc, func) => func(acc), startVal);
+}
+
+function add100(num) {
+return num + 100;
+}
+
+function divByFive(num) {
+return num / 5;
+}
+
+function multiplyByThree(num) {
+return num * 3;
+}
+
+function multiplyFive(num) {
+return num * 5;
+}
+
+function addTen(num) {
+return num + 10;
+}
+
+console.log(combineOperations(0, [add100, divByFive, multiplyByThree])); // Should output 60 -->
+console.log(combineOperations(0, [divByFive, multiplyFive, addTen])); // Should output 10

@@ -0,0 +1,16 @@
+function myFunc(array, callback) {
+for (let i = 0; i < array.length; i++) {
+if (callback(array[i])) return i;
+}
+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);
+}
+
+console.log(myFunc(numbers, isOdd)); // Output should be 1
+console.log(myFunc(evens, isOdd)); // Output should be -1

@@ -0,0 +1,16 @@
+function myForEach(array, callback) {
+for (let i = 0; i < array.length; i++) {
+callback(array[i], i, array);
+}
+}
+
+let sum = 0;
+
+function addToSum(num) {
+sum += num;
+}
+
+// /*** Uncomment these to check your work! ***/
+const nums = [1, 2, 3];
+myForEach(nums, addToSum);
+console.log(sum); // Should output 6