Coding⏱️ 1 min read📅 2026-06-03

How to Fix: Why does 'instanceof' in TypeScript give me the error "'Foo' only refers to a type, but is being used as a value here."?

Type checking issue with instanceof operator in TypeScript.

Quick Answer: The error occurs because instanceof checks if an object is an instance of a class, not if it has a specific property. Use the 'in' keyword instead to check for properties.

📋 Table of Contents

  1. 🔍 Why This Happens
  2. ✅ Best Solutions to Fix It
  3. 🎯 Final Words

The error 'Foo' only refers to a type, but is being used as a value here

🔍 Why This Happens

    ✅ Best Solutions to Fix It

    Update System Settings

      Alternative Advanced Fix

        🎯 Final Words

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