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Javascript Articles
Page 118 of 534
Search a complex object by id property in JavaScript
Suppose we have a complex JSON Object like this − const obj = { "id": "0001", "fieldName": "sample1", "fieldValue": "0001", "subList": [ { "id": 1001, "fieldName": "Sample Child 1", "fieldValue": "1001", "subList": [] }, { "id": 1002, "fieldName": "Sample Child 2", ...
Read MoreReturn indexes of greatest values in an array in JavaScript
We are required to write a JavaScript function that takes in an array of Numbers. The array may contain more than one greatest element (i.e., repeating greatest element). We are required to write a JavaScript function that takes in one such array and returns all the indices of the greatest element. Using Array.reduce() Method This approach first finds the maximum value using Math.max(), then uses reduce() to collect all indices where the element equals the maximum value. const arr = [10, 5, 4, 10, 5, 10, 6]; const findGreatestIndices = arr => { ...
Read MoreUse array as sort order in JavaScript
In JavaScript, you can sort an array of objects based on a custom order defined by another array. This is useful when you need to arrange data according to a specific sequence rather than alphabetical or numerical order. Problem Statement Given a reference array that defines the desired order and an array of objects, we need to sort the objects so their property values match the sequence in the reference array. const sort = ["this", "is", "my", "custom", "order"]; const myObjects = [ {"id":1, "content":"is"}, {"id":2, "content":"my"}, ...
Read MoreChecking if a key exists in a JavaScript object
We are required to illustrate the correct way to check whether a particular key exists in an object or not. Before moving on to the correct way let's first examine an incorrect way and see how it's actually incorrect. Way 1: Checking for undefined value (incorrect way) Due to the volatile nature of JavaScript, we might want to check for the existence of key in an object like this: const obj = { name: 'Rahul' }; // Incorrect approaches console.log(!obj['fName']); ...
Read MoreExtract arrays separately from array of Objects in JavaScript
Suppose, we have an array of objects like this − const arr = [{ name : 'Client 1', total: 900, value: 12000 }, { name : 'Client 2', total: 10, value: 800 }, { name : 'Client 3', total: 5, value : 0 }]; We are required to write a JavaScript function that takes in one such array and extracts a separate array for each object property. Therefore, ...
Read MoreFilter an array containing objects based on another array containing objects in JavaScript
Suppose we have two arrays of objects like these − const arr1 = [{id:'1', name:'A'}, {id:'2', name:'B'}, {id:'3', name:'C'}, {id:'4', name:'D'}]; const arr2 = [{id:'1', name:'A', state:'healthy'}, {id:'3', name:'C', state:'healthy'}]; We are required to write a JavaScript function that takes in two such arrays. Our function should return a new filtered version of the first array (arr1 in this case) that contains only those objects with a name property that are not contained in the second array (arr2 in this case) with the same name property. Therefore, the output, in this case, should look like ...
Read MoreIterate through Object keys and manipulate the key values in JavaScript
When working with arrays of objects in JavaScript, you often need to iterate through object keys and transform their values. This article demonstrates how to extract specific elements from array values within objects. Problem Statement Suppose we have an array of objects where each property contains an array of values: const arr = [ { col1: ["a", "b"], col2: ["c", "d"] }, { ...
Read MoreChecking for straight lines in JavaScript
We need to write a JavaScript function that takes an array of coordinate pairs and determines if all points form a straight line. Each subarray contains exactly two items representing x and y coordinates. Our function checks whether the coordinates form a straight line by calculating and comparing slopes between points. For example: [[4, 5], [5, 6]] should return true (slope = 1) [[1, 2], [2, 3], [4, 5]] should return true (all have slope = 1) [[1, 1], [2, 2], [3, 4]] should return false (different slopes) The array is guaranteed to contain ...
Read MoreFinding the power of a string from a string with repeated letters in JavaScript
The power of a string is the maximum length of a non-empty substring that contains only one unique character. We are required to write a JavaScript function that takes in a string and returns its power. For example − const str = "abbcccddddeeeeedcba" Then the output should be 5, because the substring "eeeee" is of length 5 with the character 'e' only. How It Works The algorithm traverses the string and counts consecutive identical characters. It tracks the maximum count found, which represents the power of the string. ...
Read MoreFinding day of week from date (day, month, year) in JavaScript
We are required to write a JavaScript function that takes in three arguments, namely: day, month and year. Based on these three inputs, our function should find the day of the week on that date. For example: If the inputs are − day = 15, month = 8, year = 1993 Output Then the output should be − const output = 'Sunday' Using Built-in Date Object (Simple Method) The easiest approach is to use JavaScript's built-in Date object: function getDayOfWeek(day, month, year) { ...
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