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readme changes (codesONLY#93)
* 🎨 update and clear the clutter * 📝 improve README.md * feat: add prototype, promises code snippets * feat: add prototype, promises code snippets * feat: add functions, objects, recursion etc. snippets * feat: add more snippets in objects, closures and arrays * feat: add functions code * feat: add promise pollyfils * feat: add object and functions snippets * feat: add array questions * feat: add calculator chaining code * feat: add memoize one * add more solutions snippets
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‎Snippets/Arrays/arraySubset.js‎

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const arr1 = [2, 3, 4, 5, 6, 88, 9];
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const arr2 = [3, 3, 3, 5, 100];
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function isSubset(arr1, arr2) {
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const arr1Set = [];
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const arr2Set = [];
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arr1.forEach((item) => {
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if (!arr1Set.includes(item)) {
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arr1Set.push(item);
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}
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});
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arr2.forEach((item) => {
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if (!arr2Set.includes(item)) {
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arr2Set.push(item);
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}
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});
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const res = arr1Set.reduce((previousValue, currentValue) => {
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return previousValue + +arr2Set.includes(currentValue);
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}, 0);
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return res === arr2Set.length;
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}
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console.log(isSubset(arr1, arr2));

‎Snippets/Arrays/atPolyfill.js‎

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Array.prototype.myAt = myAt;
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function myAt(index) {
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if (index >= 0) {
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return this[index];
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}
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return this[this.length - -index];
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}
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console.log([1, 2, 3].myAt(-4));

‎Snippets/Arrays/filterPolyfill.js‎

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Array.prototype.myFilter = myFilter;
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function myFilter(cb) {
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const filteredArr = [];
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this.forEach((item) => {
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if (cb(item)) {
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filteredArr.push(item);
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}
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});
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return filteredArr;
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}
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const arr = [1, 2, 3, 4];
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console.log(arr.myFilter((item) => item !== 2));

‎Snippets/Arrays/flattenADeeplyNestedArray.js‎

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function flattenArray(arr, n = Infinity) {
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let res = [];
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for (i in arr) {
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if (n !== 0 && Array.isArray(arr[i])) {
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res.push(...flattenArray(arr[i], n - 1));
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} else {
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res.push(arr[i]);
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}
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}
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return res;
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}
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let input = [
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1,
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2,
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3,
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[4],
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[5, 6, [7], [8, [9, [10]]]],
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11,
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12,
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13,
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[14, [[[[[15, [16]]]]]]],
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17,
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[19, [20, [21, [22, [23, [24, [[[[[25]]]]]]]]]]],
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];
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console.log(flattenArray(input, 2));

‎Snippets/Arrays/groupBy.js‎

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const arr = [6.1, 2.4, 2.7, 6.8];
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function groupBy(arr, property) {
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const groupByString = (arr, query) => {
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let res = {};
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arr.forEach((item, index) => {
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const queryList = query.split(".");
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let currKey;
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let currItem = item;
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let count = 0;
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for (let i = 0; i < queryList.length; i++) {
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currKey = queryList[i];
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if (!currItem[currKey]) {
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break;
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} else {
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count += 1;
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currItem = currItem[currKey];
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}
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}
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if (count !== queryList.length) {
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currItem = undefined;
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}
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if (!res[currItem]) {
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res[currItem] = [item];
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} else {
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res[currItem].push(item);
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}
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});
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return res;
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};
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const groupByCallback = (arr, cb) => {
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let res = {};
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arr.forEach((item) => {
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const ans = cb.call(null, item);
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if (Object.keys(res).includes(ans.toString())) {
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res[ans].push(item);
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} else {
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res[ans] = [item];
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}
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});
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return res;
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};
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let res;
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switch (typeof property) {
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case "function":
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res = groupByCallback(arr, property);
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break;
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case "string":
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res = groupByString(arr, property);
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break;
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default:
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return new Error("Invalid Property Type");
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}
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return res;
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}
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// groupBy(arr, Math.floor);
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console.log(groupBy(arr, Math.ceil));
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console.log(groupBy([6.1, 4.2, 6.3], Math.floor));
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console.log(groupBy(["one", "two", "three"], "length"));
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console.log(
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groupBy(
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[{ a: { b: { c: 1 } } }, { a: { b: { c: 1 } } }, { a: { b: { c: 2 } } }],
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"b.a.c"
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)
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);
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console.log(
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groupBy(
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[{ a: { b: { c: 1 } } }, { a: { b: { c: 1 } } }, { a: { b: { c: 2 } } }],
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"a.b.c"
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)
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);
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// alternate solution
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function groupByAlternative(collection, property) {
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const output = {};
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if (!collection || typeof collection !== "object") {
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return output;
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}
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const isPropertyFunction = typeof property === "function";
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const isPropertyPath = typeof property === "string";
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for (const value of Object.values(collection)) {
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let current = undefined;
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if (isPropertyFunction) {
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current = property(value);
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} else if (isPropertyPath) {
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// a.b.c -> [a, b, c];
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const path = property.split(".");
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let i;
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let currentKey;
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let currentItem = value; // { a: { b: { c: 1 } } }
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for (i = 0; i < path.length; i++) {
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// [a, b, c] -> currentKey: path[0] -> a
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// [a, b, c] -> currentKey: path[1] -> b
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// [a, b, c] -> currentKey: path[2] -> c
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currentKey = path[i];
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if (!currentItem[currentKey]) {
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currentItem = undefined;
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break;
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}
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currentItem = currentItem[currentKey];
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}
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current = currentItem;
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}
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output[current] = output[current] || [];
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output[current].push(value);
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}
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return output;
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}

‎Snippets/Arrays/mapPolyfill.js‎

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Array.prototype.myMap = myMap;
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function myMap(cb) {
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const newArr = [];
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for (let i = 0; i < this.length; i++) {
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newArr.push(cb(this[i]));
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}
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return newArr;
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}
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const arr = [1, 2, 3, 4, 5];
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console.log(arr.myMap((item) => item + 2));

‎Snippets/Arrays/pushPolyfill.js‎

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Array.prototype.myPush = myPush;
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function myPush(item) {
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this[this.length] = item;
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return this;
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}
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const arr = [1, 2, 3];
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arr.myPush(2).push(2); // chaining possible
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console.log(arr);

‎Snippets/Arrays/reducePolyfill.js‎

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Array.prototype.myReduce = myReduce;
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function myReduce(cb, initialValue = this[0]) {
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let result = initialValue;
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this.forEach((item) => {
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result = cb(result, item);
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});
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return result;
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}
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const array1 = [1, 2, 3, 4];
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const sumWithInitial = array1.myReduce(
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(previousValue, currentValue) => previousValue + currentValue,
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0
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);
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console.log(sumWithInitial);

‎Snippets/Arrays/removeDuplicates.js‎

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const arr = [1, 2, 2, 3];
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const updatedArrWithSet = [...new Set(arr)];
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const updatedArrWithFilter = arr.filter((c, index) => {
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return index !== arr.indexOf(c);
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});
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const updatedArrWithIncludes = [];
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arr.forEach((c) => {
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if (!updatedArrWithIncludes.includes(c)) {
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updatedArrWithIncludes.push(c);
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}
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});
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console.log(updatedArrWithIncludes);

‎Snippets/Arrays/unshiftPolyfill.js‎

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Array.prototype.myUnshift = myUnshift;
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function myUnshift(item) {
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let prevItem = item;
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const originalLength = this.length;
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for (let i = 0; i <= originalLength; i++) {
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let temp = this[i];
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this[i] = prevItem;
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prevItem = temp;
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}
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return this;
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}
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const arr = [1, 2, 3, 4];
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arr
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.myUnshift(2)
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.myUnshift(100)
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.myUnshift(() => console.log("WOW"));
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console.log(arr);

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