👀 Views: 82 💬 Answers: 1 📅 Created: 2025-08-21

javascript arrays map JavaScript

Can someone help me understand I'm working on a project and hit a roadblock. I'm working with an unexpected scenario while using the `Array.prototype.map()` method in JavaScript, particularly when dealing with arrays of objects. I have an array of user objects, and I want to create a new array that includes each user's name and age, but I need to ensure that the original objects remain unchanged. However, it seems that when I try to map the array, the original objects are being mutated instead of creating a new copy. Here’s the code I’m using: ```javascript const users = [ { id: 1, name: 'Alice', age: 25 }, { id: 2, name: 'Bob', age: 30 } ]; const userNamesAndAges = users.map(user => { user.age += 1; // I want to increment the age in a new array return { name: user.name, age: user.age }; }); console.log(users); // Outputs: [{ id: 1, name: 'Alice', age: 26 }, { id: 2, name: 'Bob', age: 31 }] console.log(userNamesAndAges); // Outputs: [{ name: 'Alice', age: 26 }, { name: 'Bob', age: 31 }] ``` As you can see, the original `users` array is being modified, which is not what I expected. I thought that `map()` should create a new array based on the return value of the callback function without altering the original elements. I've tried using `Object.assign()` to create a new object but still faced the same scenario. How can I modify this approach to ensure the original `users` array remains unchanged? Is there a best practice for handling such situations in JavaScript? I'm working on a CLI tool that needs to handle this. Could this be a known issue? This issue appeared after updating to Javascript latest. Any ideas what could be causing this? This is happening in both development and production on Windows 10.