👀 Views: 50 💬 Answers: 1 📅 Created: 2025-06-11

javascript array map JavaScript

I need help solving Hey everyone, I'm running into an issue that's driving me crazy. Quick question that's been bugging me - I'm working with a weird scenario while trying to transform an array using the `map` method in JavaScript... I have an array of objects, and I'm trying to create a new array based on the original one. However, it seems that my transformations are affecting the original array, which I thought wouldn't happen since `map` should return a new array. Here’s a simplified version of my code: ```javascript const originalArray = [{ id: 1, value: 10 }, { id: 2, value: 20 }]; let multiplier = 2; const newArray = originalArray.map(item => { item.value *= multiplier; // I expected this to modify the copy, not the original return { ...item, value: item.value + 5 }; // Adding 5 to the value }); console.log('Original Array:', originalArray); console.log('New Array:', newArray); ``` When I run this code, I see that the `originalArray` is mutated, and I get: ``` Original Array: [{ id: 1, value: 20 }, { id: 2, value: 40 }] New Array: [{ id: 1, value: 25 }, { id: 2, value: 45 }] ``` I thought the `map` method should return a new array without side effects on the original array. What am I missing here? How can I prevent this mutation? I’ve tried creating a deep copy of the objects using `JSON.parse(JSON.stringify(item))`, but it feels inefficient. Is there a better way to handle this situation? I'm using Node.js v16.13.1. This is part of a larger API I'm building. How would you solve this? This is part of a larger application I'm building. Cheers for any assistance!