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Javascript Articles
Page 127 of 534
How to sort a JavaScript object list based on a property when the property is not consistent
When sorting JavaScript object arrays with inconsistent properties, you need a custom comparator function. This scenario commonly occurs when some objects have date values while others have null or undefined dates. The requirement is to display objects without dates at the top (sorted alphabetically by name), followed by objects with dates (sorted chronologically). Problem Overview Consider an array where some objects have date properties and others don't: const items = [ { name: "Charlie", date: "2024-03-15" }, { name: "Alice", date: null }, ...
Read MoreConvert 2d tabular data entries into an array of objects in JavaScript
Converting 2D tabular data into an array of objects is a common requirement when working with datasets. This transformation groups rows by a unique identifier and creates objects with dynamic properties. Problem Overview Suppose we have an array of arrays representing tabular data: const arr = [ ["Ashley", "2017-01-10", 80], ["Ashley", "2017-02-10", 75], ["Ashley", "2017-03-10", 85], ["Clara", "2017-01-10", 90], ["Clara", "2017-02-10", 82] ]; We need to transform this into an array of objects where each unique name becomes a ...
Read MoreBest way to flatten an object with array properties into one array JavaScript
When you have an object containing arrays as values, you often need to flatten all these arrays into a single array. This is a common operation when working with grouped data. const obj = { arr_a: [9, 3, 2], arr_b: [1, 5, 0], arr_c: [7, 18] }; console.log("Original object:", obj); Original object: { arr_a: [ 9, 3, 2 ], arr_b: [ 1, 5, 0 ], arr_c: [ 7, 18 ] } The goal is to merge all array values into one ...
Read MoreSubtracting array in JavaScript Delete all those elements from the first array that are also included in the second array
Subtracting arrays in JavaScript involves removing all elements from the first array that exist in the second array. This operation is useful for filtering data and finding differences between datasets. Problem Statement Given two arrays, we need to delete all elements from the first array that are also present in the second array. const arr1 = ['uno', 'dos', 'tres', 'cuatro']; const arr2 = ['dos', 'cuatro']; // Expected output: ['uno', 'tres'] Using filter() with indexOf() The filter() method creates a new array with elements that pass a test. We use indexOf() to check ...
Read MoreJavaScript: compare array element properties, and if identical, combine
When working with arrays of objects, you often need to combine objects that have identical properties. In this example, we'll consolidate storage devices with the same size by adding up their counts. Suppose we have an array of objects containing information about data storage devices: const drives = [ {size:"900GB", count:3}, {size:"900GB", count:100}, {size:"1200GB", count:5}, {size:"900GB", count:1} ]; console.log("Original array:", drives); Original array: [ { size: '900GB', count: 3 }, { size: '900GB', count: ...
Read MoreImplementing Math function and return m^n in JavaScript
We are required to write a JavaScript function that takes in two numbers say m and n. Then function should calculate and return m^n. For example − For m = 4, n = 3, then power(4, 3) = 4^3 = 4 * 4 * 4 = 64 power(6, 3) = 216 Using Built-in Math.pow() Method JavaScript provides the built-in Math.pow() method for calculating powers: console.log(Math.pow(4, 3)); // 4^3 console.log(Math.pow(6, 3)); // 6^3 console.log(Math.pow(2, -2)); // 2^(-2) = 1/4 64 216 0.25 Custom Implementation Using Recursion ...
Read MoreFinding the sub array that has maximum sum JavaScript
We are required to write a JavaScript function that takes in an array of numbers. The array can contain both positive and negative numbers. The purpose of our function is to find the subarray (of any length) whose elements when summed give the maximum sum. This problem is known as the Maximum Subarray Problem and is commonly solved using Kadane's Algorithm. For example, if the input array is: const arr = [-2, 1, -3, 4, -1, 2, 1, -5, 4]; Then the output should be: 6 Because the subarray [4, ...
Read MoreDifference between two strings JavaScript
We are given two strings, say s and t. String t is generated by random shuffling string s and then add one more letter at a random position. We are required to write a JavaScript function that takes both these strings and returns the letter that was added to t. For example − If the input strings are − const s = "abcd", t = "abcde"; Then the output should be − const output = "e"; because 'e' is the letter that was added. Method 1: Using XOR ...
Read MoreChecking for overlapping times JavaScript
Time interval overlap detection is a common programming challenge. We need to determine if any two time intervals in an array share common time periods. Problem Definition Given an array of time intervals with start and end times, we need to check if any two intervals overlap. Two intervals overlap when they have some time in common. const arr = [ { start: '01:00', end: '04:00' }, { start: '05:00', end: '08:00' }, { start: '07:00', end: '11:00' }, { start: '09:30', end: '18:00' ...
Read MoreSorting an array of objects by an array JavaScript
In JavaScript, you can sort an array of objects based on the order defined by another array. This is useful when you need to prioritize objects according to a specific sequence. Problem Statement Given an array of objects and a reference array, we need to sort the objects according to the order specified in the reference array. const orders = [ { status: "pending"}, { status: "received" }, { status: "sent" }, { status: "pending" } ]; const statuses = ...
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