👀 Views: 44 💬 Answers: 1 📅 Created: 2025-06-02

javascript arrays performance JavaScript

This might be a silly question, but I'm working on a JavaScript project where I need to manage a sparse array and I'm unsure about the best approach. The array will contain a lot of `undefined` values interspersed with some actual numbers, and I'm working with performance optimization when trying to iterate over it with methods like `forEach` or `map`. Here's what I've been doing: ```javascript const sparseArray = []; // Adding values sparsely sparseArray[100] = 1; sparseArray[200] = 2; sparseArray[300] = 3; ``` When I try to log values using `sparseArray.forEach`, I get an unexpected output that includes many `undefined` entries, which makes processing slower: ```javascript sparseArray.forEach(value => { if (value !== undefined) { console.log(value); } }); // Outputs 1, 2, 3, but has to skip many undefined ``` I've read that using an object might be more efficient in terms of storage and iteration, like this: ```javascript const sparseObject = { 100: 1, 200: 2, 300: 3 }; ``` When I access the values using `Object.keys(sparseObject).forEach`, it seems much faster: ```javascript Object.keys(sparseObject).forEach(key => { console.log(sparseObject[key]); // Outputs 1, 2, 3 }); ``` Now I'm torn between sticking with the array or switching to the object. What are the performance implications of using one over the other in JavaScript, particularly in terms of memory usage and speed during iteration? Is there a best practice for this kind of scenario?