Coding⏱️ 3 min read📅 2026-06-04

How to Fix: Error while sorting array of objects Cannot assign to read only property '2' of object '[object Array]'

Error while sorting array of objects Cannot assign to read only property '2' of object '[object Array]'

Quick Answer: The issue arises from trying to sort an array of objects directly. Use the spread operator or destructuring to fix it.

📋 Table of Contents

  1. ⚠️ Common Causes
  2. 🛠️ Step-by-Step Verified Fixes
  3. 🎯 Final Words

The error 'Cannot assign to read only property '2' of object '[object Array]''' occurs when attempting to sort an array of objects using the `sort()` method. This issue affects developers who are unfamiliar with JavaScript's nuances or those working with legacy codebases.

This error can be frustrating, especially when trying to implement a seemingly simple task like sorting data. However, understanding the root cause and applying the correct solution will resolve the issue.

⚠️ Common Causes

  • The primary reason for this error is that the `sort()` method is being called on an array literal, which returns a new array object instead of modifying the original array. This causes the error because arrays are not objects in JavaScript, and attempting to assign to a read-only property results in the error.
  • Another possible cause is that the array contains other types of data besides objects, which can lead to unexpected behavior when trying to sort.

🛠️ Step-by-Step Verified Fixes

Using the `Array.prototype.sort()` method with an arrow function

  1. Step 1: Replace the original `sort()` call with the following code: `array.sort((a, b) => { return b.stats.speed - a.stats.speed });` This ensures that the correct array object is being sorted.
  2. Step 2: Verify that the array only contains objects and that all properties are numeric. If the array contains non-numeric values, consider using a different sorting method or data transformation.
  3. Step 3: Test the code to ensure it produces the desired output.

Using the `Array.prototype.sort()` method with a traditional function

  1. Step 1: Replace the original `sort()` call with the following code: `array.sort(function(a, b) { return b.stats.speed - a.stats.speed; });` This ensures that the correct array object is being sorted.
  2. Step 2: Verify that the array only contains objects and that all properties are numeric. If the array contains non-numeric values, consider using a different sorting method or data transformation.
  3. Step 3: Test the code to ensure it produces the desired output.

🎯 Final Words

By understanding the root cause of the error and applying one of the provided solutions, developers can resolve the 'Cannot assign to read only property '2' of object '[object Array]''' issue. Remember to always verify that your array contains only objects with numeric properties when sorting.

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