👀 Views: 87 💬 Answers: 1 📅 Created: 2025-06-12

javascript arrays merge

I'm trying to merge two arrays of objects based on a unique identifier, but I'm encountering unexpected behavior when there are overlapping properties... My goal is to create a new array that contains unique objects, where properties from the second array should overwrite those from the first if they share the same identifier. Here's the code I've written: ```javascript const array1 = [ { id: 1, name: 'Alice', age: 25 }, { id: 2, name: 'Bob', age: 30 }, ]; const array2 = [ { id: 2, name: 'Robert', age: 35 }, { id: 3, name: 'Charlie', age: 28 }, ]; const mergeArrays = (arr1, arr2) => { const merged = [...arr1]; arr2.forEach(item => { const index = merged.findIndex(el => el.id === item.id); if (index !== -1) { merged[index] = { ...merged[index], ...item }; } else { merged.push(item); } }); return merged; }; console.log(mergeArrays(array1, array2)); ``` When I run this code, I expected the output to be: ```javascript [ { id: 1, name: 'Alice', age: 25 }, { id: 2, name: 'Robert', age: 35 }, { id: 3, name: 'Charlie', age: 28 } ] ``` Instead, I'm getting: ```javascript [ { id: 1, name: 'Alice', age: 25 }, { id: 2, name: 'Alice', age: 25 }, { id: 3, name: 'Charlie', age: 28 } ] ``` It seems like the properties from the second array are not merging correctly. I've also tried using `Object.assign()` but that gives me the same result. I'm using Node.js v14.17.0. Any ideas on what I might be missing or if there's a more efficient way to achieve this? I'm coming from a different tech stack and learning Javascript. Any advice would be much appreciated. I'm on macOS using the latest version of Javascript. Any help would be greatly appreciated!