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Javascript Articles
Page 280 of 534
Nested collection filter with JavaScript
Suppose, we have an array of nested objects like this −const arr = [{ id: 1, legs:[{ carrierName:'Pegasus' }] }, { id: 2, legs:[{ carrierName: 'SunExpress' }, { carrierName: 'SunExpress' }] }, { id: 3, legs:[{ carrierName: 'Pegasus' }, { carrierName: 'SunExpress' }] }];We are required to write a JavaScript function that takes one such array as the first argument and a search query string as the second argument.Our function should filter ...
Read MoreBuild tree array from JSON in JavaScript
Suppose, we have the following array in JavaScript −const arr = [{ "code": "2", "name": "PENDING" }, { "code": "2.2", "name": "PENDING CHILDREN" }, { "code": "2.2.01.01", "name": "PENDING CHILDREN CHILDREN" }, { "code": "2.2.01.02", "name": "PENDING CHILDREN CHILDREN02" }, { "code": "1", "name": "ACTIVE" }, { "code": "1.1", "name": "ACTIVE CHILDREN" }, { "code": "1.1.01", "name": "ACTIVE CHILDREN CHILDREN" }];We are required to write a JavaScript function that takes in one such array. The function should build a tree structure from this array based on ...
Read MoreSum identical elements within one array in JavaScript
We are required to write a JavaScript function that takes in an array of Numbers.The array might contain some repeating / duplicate entries within it. Our function should add all the duplicate entries and return the new array thus formed.ExampleThe code for this will be −const arr = [20, 20, 20, 10, 10, 5, 1]; const sumIdentical = (arr = []) => { let map = {}; for (let i = 0; i < arr.length; i++) { let el = arr[i]; map[el] = map[el] ? map[el] + 1 : 1; }; const res = []; for (let count in map) { res.push(map[count] * count); }; return res; }; console.log(sumIdentical(arr));OutputAnd the output in the console will be −[ 1, 5, 20, 60 ]
Read MoreGrouping an Array and Counting items creating new array based on Groups in JavaScript
Suppose, we have an array of objects like this −const arr = [ { region: "Africa", fruit: "Orange", user: "Gary" }, { region: "Africa", fruit: "Apple", user: "Steve" }, { region: "Europe", fruit: "Orange", user: "John" }, { region: "Europe", fruit: "Apple", user: "bob" }, { region: "Asia", fruit: "Orange", user: "Ian" }, { region: "Asia", fruit: "Apple", user: "Angelo" }, { region: "Africa", fruit: "Orange", user: "Gary" } ];We are required to write a JavaScript function that takes in one such array. The function should prepare a new array of objects that ...
Read MoreConvert JSON array into normal json in JavaScript
Suppose, we have a JSON array with key/value pair objects like this −const arr = [{ "key": "name", "value": "john" }, { "key": "number", "value": "1234" }, { "key": "price", "value": [{ "item": [{ "item": [{ "key": "quantity", "value": "20" }, { "key": "price", "value": "200" }] }] ...
Read MoreBuild tree array from flat array in JavaScript
We have a complex json file that we have to handle with JavaScript to make it hierarchical, in order to later build a tree.Every entry of the JSON array has −id − a unique id, parentId − the id of the parent node (which is 0 if the node is a root of the tree)level − the level of depth in the treeThe JSON data is already "ordered", means that an entry will have above itself a parent node or brother node, and under itself a child node or a brother node.The input array is −const arr = [ ...
Read MoreTransform data from a nested array to an object in JavaScript
Suppose, we have the following array of arrays −const arr = [ [ ['dog', 'Harry'], ['age', 2] ], [ ['dog', 'Roger'], ['age', 5] ] ];We are required to write a JavaScript function that takes in one such nested array. The function should then prepare an object based on the array.The object for the above array should look like −const output = [ {dog: 'Harry', age: 2}, {dog: 'Roger', age: 5} ];ExampleThe code for this will be −const arr = [ [ ['dog', 'Harry'], ['age', ...
Read MoreCounting the occurrences of JavaScript array elements and put in a new 2d array
We are required to write a JavaScript function that takes in an array of literal values. The function should then count the frequency of each element of the input array and prepare a new array on that basis.For example − If the input array is −const arr = [5, 5, 5, 2, 2, 2, 2, 2, 9, 4];Then the output should be −const output = [ [5, 3], [2, 5], [9, 1], [4, 1] ];ExampleThe code for this will be −const arr = [5, 5, 5, 2, 2, 2, 2, 2, 9, 4]; const frequencyArray = (arr = []) => { const res = []; arr.forEach(el => { if (!this[el]) { this[el] = [el, 0]; res.push(this[el]) }; this[el][1] ++ }, {}); return res; }; console.log(frequencyArray(arr));OutputAnd the output in the console will be −[ [ 5, 3 ], [ 2, 5 ], [ 9, 1 ], [ 4, 1 ] ]
Read MoreTest for existence of nested JavaScript object key in JavaScript
Suppose, we have a reference to an object −let test = {};This object will potentially (but not immediately) have nested objects, something like −test = {level1: {level2: {level3: "level3"}}};We are required to write a JavaScript function that takes in one such object as the first argument and then any number of key strings as the arguments after.The function should determine whether or not the nested combination depicted by key strings exist in the object.ExampleThe code for this will be −const checkNested = function(obj = {}){ const args = Array.prototype.slice.call(arguments, 1); for (let i = 0; i < args.length; ...
Read MoreCounting number of vowels in a string with JavaScript
We are required to write a JavaScript function that takes in a string. The function should count the number of vowels present in the string.The function should prepare an object mapping the count of each vowel against them.ExampleThe code for this will be −const str = 'this is an example string'; const vowelCount = (str = '') => { const splitString=str.split(''); const obj={}; const vowels="aeiou"; splitString.forEach((letter)=>{ if(vowels.indexOf(letter.toLowerCase()) !== -1){ if(letter in obj){ obj[letter]++; }else{ ...
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