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Javascript Articles
Page 347 of 534
How to unflatten a JavaScript object in a daisy-chain/dot notation into an object with nested objects and arrays?
Suppose, we have an object like this −const obj = { "firstName": "John", "lastName": "Green", "car.make": "Honda", "car.model": "Civic", "car.revisions.0.miles": 10150, "car.revisions.0.code": "REV01", "car.revisions.0.changes": "", "car.revisions.1.miles": 20021, "car.revisions.1.code": "REV02", "car.revisions.1.changes.0.type": "asthetic", "car.revisions.1.changes.0.desc": "Left tire cap", "car.revisions.1.changes.1.type": "mechanic", "car.revisions.1.changes.1.desc": "Engine pressure regulator", "visits.0.date": "2015-01-01", "visits.0.dealer": "DEAL-001", "visits.1.date": "2015-03-01", "visits.1.dealer": "DEAL-002" };We are required to write a JavaScript function that takes in one such object and unflattens it into nested objects and arrays.Therefore, ...
Read MoreFind the least duplicate items in an array JavaScript
We are required to write a JavaScript function that takes in an array of literals which may contain some duplicate values.The function should return an array of all those elements that are repeated for the least number of times.For example− If the input array is −const arr = [1, 1, 2, 2, 3, 3, 3];Then the output should be −const output = [1, 2];because 1 and 2 are repeated for the least number of times (2)Exampleconst arr = [1, 1, 2, 2, 3, 3, 3]; const getLeastDuplicateItems = (arr = []) => { const hash = Object.create(null); let ...
Read MoreTransforming array to object JavaScript
Suppose we have an array of strings like this −const arr = [ 'type=A', 'day=45' ];We are required to write a JavaScript function that takes in one such array. The function should construct an object based on this array. The object should contain a key/value pair for each string in the array.For any string, the part before '=' becomes the key and the part after it becomes the value.Exampleconst arr = [ 'type=A', 'day=45' ]; const arrayToObject = (arr = []) => { const obj = {}; for (let i = 0; i < arr.length; i++) { ...
Read MoreFinding the majority element of an array JavaScript
We are given an array of size n, and we are required to find the majority element. The majority element is the element that appears more than [ n/2 ] times.Exampleconst arr = [2, 4, 2, 2, 2, 4, 6, 2, 5, 2]; const majorityElement = (arr = []) => { const threshold = Math.floor(arr.length / 2); const map = {}; for (let i = 0; i < arr.length; i++) { const value = arr[i]; map[value] = map[value] + 1 || 1; if (map[value] > threshold) return value }; return false; }; console.log(majorityElement(arr));OutputAnd the output in the console will be −2
Read MoreFinding sum of a range in an array JavaScript
We are required to write an Array function (functions that lives on Array.prototype object). The function should take in a start index and an end index and it should sum all the elements from start index to end index in the array (including both start and end)Exampleconst arr = [1, 2, 3, 4, 5, 6, 7]; const sumRange = function(start = 0, end = 1){ const res = []; if(start > end){ return res; }; for(let i = start; i
Read MoreDynamic Programming: Is second string subsequence of first JavaScript
We are given two strings str1 and str2, we are required to write a function that checks if str1 is a subsequence of str2.A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters.For example, "ace" is a subsequence of "abcde" while "aec" is notExampleconst str1 = 'ace'; const str2 = 'abcde'; const isSubsequence = (str1, str2) => { let i=0; let j=0; while(i
Read MoreSort array according to the date property of the objects JavaScript
We are required to write a JavaScript function that takes in an array of objects of dates like this −const arr = [ {date: "2016-06-08 18:10:00"}, {date: "2016-04-26 20:01:00"}, {date: "2017-02-06 14:38:00"}, {date: "2017-01-18 17:30:21"}, {date: "2017-01-18 17:24:00"} ];We are required to write a JavaScript function that takes in one such array. The function should then sort the array according to the date property of the objects.Exampleconst arr = [ {date: "2016-06-08 18:10:00"}, {date: "2016-04-26 20:01:00"}, {date: "2017-02-06 14:38:00"}, {date: "2017-01-18 17:30:21"}, {date: "2017-01-18 17:24:00"} ]; const sortByTime = (arr ...
Read MoreMerge JSON array date based JavaScript
Suppose, we have the following array of objects −const arr = [ { "date" : "2010-01-01", "price" : 30 }, { "date" : "2010-02-01", "price" : 40 }, { "date" : "2010-03-01", "price" : 50 }, { "date" : "2010-01-01", "price2" : 45 }, { "date" : "2010-05-01", "price2" : 40 }, { "date" : "2010-10-01", ...
Read MoreMerge JavaScript objects with the same key value and count them
Suppose, we have an array of objects like this −const arr = [{ "value": 10, "id": "111", "name": "BlackCat", }, { "value": 10, "id": "111", "name": "BlackCat", }, { "value": 15, "id": "777", "name": "WhiteCat", }];We are required to write a JavaScript function that takes in one such array.The function should then merge all those objects together that have the common value for "id" property.Therefore, for the above array, the output should look like −const output = [{ "value": 10, "id": "111", "name": "BlackCat", "count": 2, ...
Read MoreIs the second string a rotated version of the first string JavaScript
We are required to write a JavaScript function that takes in two strings, say str1 and str2. We are required to determine whether or not the second string is a rotated version of the first string.For example− If the input strings are −const str1 = 'abcde'; const str2 = 'cdeab';Then the output should be true because str2 is indeed made by shifting 'ab' to the end of string in str1.Exampleconst str1 = 'abcde'; const str2 = 'cdeab'; const isRotated = (str1, str2) => { if(str1.length !== str2.length){ return false }; if( (str1.length || str2.length) ...
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