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Front End Technology Articles
Page 222 of 652
How to find all partitions of a multiset, where each part has distinct elements in JavaScript
Finding all partitions of a multiset where each part contains distinct elements is a complex combinatorial problem. We need to create an algorithm that generates all possible ways to divide elements into groups without repetition within each group. Let's say we have an array with repeated elements: const arr = [A, A, B, B, C, C, D, E]; We need to find all combinations that use the entire array, where no elements are repeated within each partition. Example Partitions [A, B, C, D, E] [A, B, C] [A, B, C, D] [A, ...
Read MoreFind all occurrences of a word in array in JavaScript
When working with arrays in JavaScript, you might need to find how many elements contain a specific word or substring. This article demonstrates multiple approaches to count occurrences of a word within array elements. Problem Statement We need to write a JavaScript function that takes an array of strings as the first argument and a search word as the second argument. The function should return the count of array elements that contain the specified word. Method 1: Using filter() and indexOf() This approach uses filter() to find matching elements and returns the length of the filtered ...
Read MoreSorting array of strings having year and month in JavaScript
Suppose, we have an array of strings that contains month-year combined strings like this: const arr = ["2009-feb", "2009-jan", "2010-mar", "2010-jan", "2011-jul", "2011-sep", "2011-jan", "2012-jan", "2012-dec", "2012-feb", "2013-may", "2013-jul", "2013-jun", "2014-jan", "2014-dec", "2014-may", "2015-may", "2015-jan", "2015-jun", "2016-jan", "2016-dec"]; We need to write a JavaScript function that takes such an array and sorts these dates from oldest to latest order. Approach The solution involves creating a custom sorting function that: Splits each date string to separate year and month Converts month names to numeric values ...
Read MoreCompute cartesian product of elements in an array in JavaScript
The Cartesian product of two sets (arrays) A and B, denoted A × B, is the set (array) of all ordered pairs (a, b) where a is in A and b is in B. In simpler terms, a cartesian product of two arrays is a permutation of all possible arrays of two elements whose first element belongs to the first array and the second element belongs to the second array. Example of Cartesian Product If the two arrays are: const arr1 = [1, 2, 3]; const arr2 = [4, 5]; Then their cartesian ...
Read MoreGroup by JavaScript Array Object
Suppose we have an array of arrays that contains the marks of some students in some subjects like this − const arr = [ ["English", 52], ["Hindi", 154], ["Hindi", 241], ["Spanish", 10], ["French", 65], ["German", 98], ["Russian", 10] ]; We are required to write a JavaScript function that takes in one such array and returns an object of objects. The return object should contain an object for each unique subject, and that object should contain information like the number of appearances ...
Read MoreHow to count the occurrence of a specific string in a string in JavaScript
In JavaScript, counting occurrences of a substring within a string is a common task. There are several approaches to accomplish this, from simple loops to built-in string methods. For example, counting how many times "is" appears in "this is a string" should return 2. count('this is a string', 'is') should return 2; Method 1: Using indexOf() with Loop The most reliable approach uses indexOf() to find each occurrence and increment a counter: const str1 = 'this is a string'; const str2 = 'is'; function countOccurrences(mainStr, subStr) { ...
Read MoreIterating through an array, adding occurrences of a true in JavaScript
Suppose we have an array of true/false values represented by 't'/'f' which we retrieved from some database like this − const arr = ['f', 't', 'f', 't', 't', 't', 'f', 'f', 't', 't', 't', 't', 't', 't', 'f', 't']; console.log(arr); [ 'f', 't', 'f', 't', 't', 't', 'f', 'f', 't', 't', 't', 't', 't', 't', 'f', 't' ] We need to count consecutive occurrences of 't' that are sandwiched between two 'f's and return an array of those counts. Array: ['f', 't', 'f', 't', 't', 't', 'f', 'f', 't', ...
Read MoreFind specific key value in array of objects using JavaScript
When working with JavaScript objects containing arrays of nested objects, you often need to find which parent key contains an object with specific property values. This is common when dealing with product catalogs, user groups, or categorized data. Example Data Structure Consider this product catalog object where each category contains an array of products: const obj = { "LAPTOP": [{ "productId": "123" }], "DESKTOP": [{ "productId": "456" ...
Read MoreSum of array object property values in new array of objects in JavaScript
When working with arrays of objects, we often need to group objects by a common property and sum up their numeric values. This is particularly useful when dealing with student records, sales data, or any scenario where duplicate categories need to be consolidated. Suppose we have an array of objects that contains data about students and their marks: const arr = [ { subject: 'Maths', marks: '40', noOfStudents: '5' }, { subject: 'Science', marks: '50', noOfStudents: '16' }, { subject: 'History', marks: '35', noOfStudents: '23' }, { subject: 'Science', ...
Read MoreCalculating Josephus Permutations efficiently in JavaScript
This problem takes its name from arguably the most important event in the life of the ancient historian Josephus. According to his tale, he and his 40 soldiers were trapped in a cave by the Romans during a siege. Refusing to surrender to the enemy, they instead opted for mass suicide, with a twist — they formed a circle and proceeded to kill one man every three, until one last man was left (and that it was supposed to kill himself to end the act). Josephus and another man were the last two and, as we now know ...
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