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Front End Technology Articles
Page 231 of 652
Grouping an Array and Counting items creating new array based on Groups in JavaScript
When working with arrays of objects in JavaScript, you often need to group data by specific properties and count unique items. This article demonstrates how to group an array by region and count unique users per region. Problem Statement Suppose we have an array of objects representing user data across different regions: const arr = [ { region: "Africa", fruit: "Orange", user: "Gary" }, { region: "Africa", fruit: "Apple", user: "Steve" }, { region: "Europe", fruit: "Orange", user: "John" }, ...
Read MoreBuild tree array from JSON in JavaScript
Building a tree structure from a flat array is a common task in JavaScript. When you have hierarchical data represented as a flat array with codes indicating parent-child relationships, you can transform it into a nested tree structure. The Problem Suppose we have the following flat array where the code property indicates hierarchy through dot notation: const arr = [{ "code": "2", "name": "PENDING" }, { "code": "2.2", "name": "PENDING CHILDREN" }, { "code": "2.2.01.01", ...
Read MoreNested collection filter with JavaScript
Filtering nested collections in JavaScript requires searching through objects that contain arrays of other objects. Let's explore how to filter an array based on properties within nested objects. The Problem Suppose we have an array of nested objects where each object contains a legs array with carrier information: const arr = [{ id: 1, legs:[{ carrierName:'Pegasus' }] }, { id: 2, legs:[{ carrierName: 'SunExpress' }, ...
Read MoreCreate an object based on 2 others in JavaScript
In JavaScript, you often need to combine properties from multiple objects into a new one. There are several modern approaches to achieve this without modifying the original objects. Problem Statement Given two objects with properties and methods, we want to create a third object that contains all properties from both: const a = { a: 1, af: function() { console.log(this.a) }, }; const b = { b: 2, bf: function() { console.log(this.b) }, }; // Goal: Create object ...
Read MoreData manipulation with JavaScript
When working with data arrays, you often need to combine different datasets. This tutorial shows how to merge a months array with a cashflows array to create a complete dataset with all months represented. Problem Statement Suppose we have two arrays describing cashflow data: const months = ["jan", "feb", "mar", "apr"]; const cashflows = [ {'month':'jan', 'value':10}, {'month':'mar', 'value':20} ]; console.log("Months:", months); console.log("Cashflows:", cashflows); Months: [ 'jan', 'feb', 'mar', 'apr' ] Cashflows: [ { month: 'jan', value: 10 }, { month: 'mar', value: 20 ...
Read MoreFind all disjointed intersections in a set of vertical line segments in JavaScript
We have a set of vertical regions defined by y1 and y2 coordinates, where y1 is the starting point and y2 is the ending point of each region. The origin of our coordinates system is the top-left corner, so y2 is always greater than y1. This is an example: const regions = [ [10, 100], [50, 120], [60, 180], [140, 220] ]; console.log(regions); [ [ 10, 100 ], [ 50, 120 ], [ 60, 180 ], [ ...
Read MoreEfficient algorithm for grouping elements and counting duplicates in JavaScript
When working with arrays of objects in JavaScript, you often need to group elements based on shared properties and count duplicates. This is common in data processing tasks like analyzing user activity, inventory management, or survey results. Problem Overview Given an array of objects, we want to group them by a specific property and count how many times each group appears. For example, if we have objects with properties like coordinates or identifiers, we can group by the first property and display counts. Original data: X A B O Y X Z I Y ...
Read MoreMost efficient method to groupby on an array of objects - JavaScript
Grouping arrays of objects is a common task in JavaScript data processing. We'll explore efficient methods to group objects by single or multiple properties and aggregate values. Sample Data Let's start with an array of objects representing project phases, steps, and tasks: const arr = [ { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" }, { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" }, { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" ...
Read MoreGet the smallest array from an array of arrays in JavaScript
When working with nested arrays in JavaScript, you might need to find the smallest subarray based on the number of elements. This is useful for data processing, filtering operations, or when you need to identify the shortest path or sequence. Suppose we have a nested array of arrays like this: const arr = [ ["LEFT", "RIGHT", "RIGHT", "BOTTOM", "TOP"], ["RIGHT", "LEFT", "TOP"], ["TOP", "LEFT"] ]; console.log("Original array:", arr); Original array: [ [ 'LEFT', 'RIGHT', 'RIGHT', 'BOTTOM', 'TOP' ], ...
Read MoreSorting an array by price in JavaScript
Sorting an array of objects by price is a common requirement in JavaScript applications. This article demonstrates how to sort house data by price values stored as strings. Sample Data Let's start with an array of house objects where prices are stored as strings: const arr = [ { "h_id": "3", "city": "Dallas", "state": "TX", "zip": "75201", ...
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