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Javascript Articles
Page 291 of 534
Iterating through an array, adding occurrences of a true in JavaScript
Suppose we have an array of true/false 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'];We are required to write a JavaScript function that takes in one such array. Our function should count the consecutive appearances of those 't' that are sandwiched between two 'f's and return an array of that count.Therefore, for the above array, the output should look like −const output = [1, 3, 6, 1];ExampleThe code for this will be −const arr = ['f', 't', 'f', ...
Read MoreHow to count the occurrence of a specific string in a string in JavaScript
We are required to write a JavaScript function that takes in two strings, say str1 and str2. The function should then count and return the number of times str2 appears in str1'For example −count('this is a string', 'is') should return 2;ExampleThe code for this will be −const str1 = 'this is a string'; const str2 = 'is'; const countOccurrences = (str1, str2, allowOverlapping = true) => { str1 += ""; str2 += ""; if (str2.length = 0) { ++n; pos += step; } else break; } return n; }; console.log(countOccurrences(str1, str2));OutputAnd the output in the console will be −2
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 of that language, sum of total marks and the average.ExampleThe code for this will be −const arr = [ ["English", 52], ...
Read MoreCompute cartesian product of elements in an array in JavaScript
Cartesian ProductThe 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.For example − If the two arrays are −const arr1 = [1, 2, 3]; const arr2 = [4, 5];Then their cartesian product will be −const product = [[1, 4], [1, 5], ...
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 are required to write a JavaScript function that takes in one such array and sorts these dates in oldest to latest order.ExampleThe code for this will be −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"]; const sorter = (a, b) => { const getDate = ...
Read MoreHow to find all partitions of a multiset, where each part has distinct elements in JavaScript
Let's say we have such an array −const arr = [A, A, B, B, C, C, D, E];We are required to create an algorithm so that it will find all the combinations that add up to the whole array, where none of the elements are repeated.Example combinations −[A, B, C, D, E] [A, B, C] [A, B, C, D] [A, B, C, E] [A, B, C] [A, B, C] [D, E]Explanation[A, B, C] [A, B, C] [D, E] and [A, B, C] [D, E] [A, B, C] are the same combinations. Also, the ordering with the subsets doesn't matter as ...
Read MoreFind all occurrences of a word in array in JavaScript
We are required to write a JavaScript function that takes in an array of literals as the first argument and a string as the second argument. Our function should return the count of the number of times that string (provided by second argument) appears anywhere in the array.ExampleThe code for this will be −const arr = ["word", "a word", "another word"]; const query = "word"; const findAll = (arr, query) => { let count = 0; count = arr.filter(el => { return el.indexOf(query) != -1; }).length; return count; }; console.log(findAll(arr, query));OutputAnd the output in the console will be −3
Read MoreGroup Similar Items in JSON in JavaScript
Suppose, we have a JSON Array that contains data about some tickets like this −const arr = [ { "quantity": "1", "description": "VIP Ticket to Event" }, { "quantity": "1", "description": "VIP Ticket to Event" }, { "quantity": "1", "description": "VIP Ticket to Event" }, { "quantity": "1", "description": "Regular Ticket to Event" }, { "quantity": "1", "description": "Regular Ticket to ...
Read MoreMultiply and Sum Two Arrays in JavaScript
We are required to write a JavaScript function that takes in two arrays of equal length. The function should multiply the corresponding (by index) values in each, and sum the results.For example: If the input arrays are −const arr1 = [2, 3, 4, 5]; const arr2 = [4, 3, 3, 1];then the output should be 34, because,(4*2+3*3+4*3+5*1) = 34ExampleThe code for this will be −const arr1 = [2, 3, 4, 5]; const arr2 = [4, 3, 3, 1]; const produceAndAdd = (arr1 = [], arr2 = []) => { let sum = 0; for(let i=0; i < arr1.length; i++) { const product = (arr1[i] * arr2[i]); sum += product; }; return sum; }; console.log(produceAndAdd(arr1, arr2));OutputAnd the output in the console will be −34
Read MoreEvaluating a string as a mathematical expression in JavaScript
We are required to write a JavaScript function that takes in a stringified mathematical equation. The function should return the result of the equation provided to the function.For example: If the equation is −const str = '1+23+4+5-30';Then the output should be 3ExampleThe code for this will be −const str = '1+23+4+5-30'; const compute = (str = '') => { let total = 0; str = str.match(/[+\−]*(\.\d+|\d+(\.\d+)?)/g) || []; while (str.length) { total += parseFloat(str.shift()); }; return total; }; console.log(compute(str));OutputAnd the output in the console will be −3
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