🔧 Error Fixes
· 1 min read

JavaScript: Cannot Read Properties of Undefined — How to Fix It

TypeError: Cannot read properties of undefined (reading 'name')

You’re accessing a property on something that’s undefined.

Fix 1: Check the variable exists

// ❌ user is undefined
console.log(user.name);

// ✅ Check first
if (user) {
  console.log(user.name);
}

// ✅ Optional chaining
console.log(user?.name);

Fix 2: Wrong object path

// ❌ data.response doesn't exist
const name = data.response.user.name;

// ✅ Check each level
const name = data?.response?.user?.name ?? 'Unknown';

Fix 3: Async data not loaded yet

// ❌ Data hasn't loaded
const [user, setUser] = useState();
return <p>{user.name}</p>;

// ✅ Handle loading state
if (!user) return <p>Loading...</p>;
return <p>{user.name}</p>;

Related: Maximum Call Stack Size Exceeded — How to Fix It

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