Software⏱️ 2 min read📅 2026-05-29

How to Fix: TypeError: Cannot read private member from an object whose class did not de

Learn how to fix: TypeError: Cannot read private member from an object whose class did not declare it when wrapping instance in Proxy.

Quick Answer: Try checking your system settings or restarting.

To fix the issue of accessing private fields in modern classes using native private fields, you need to use the `apply` method on your proxy wrapper. This allows you to capture the call object and its arguments, which are necessary for logging the execution time.

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  • [Cause]

✅ Best Solutions to Fix It

Method 1: Using `apply` on Proxy Wrapper

  1. Step 1: Create a proxy wrapper that uses `apply` to capture the call object and its arguments.

Method 2: Using `get` and `set` Traps

  1. Step 1: Create a proxy wrapper that uses `get` and `set` traps to capture the access to private fields.

🎯 Final Words

By applying these solutions, you can successfully fix the issue of accessing private fields in modern classes using native private fields.

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