Quick Answer

Fix TypeError when accessing properties of undefined/null.

Understanding the Issue

This common error occurs when trying to access a property or method of an undefined or null value. It typically indicates incomplete initialization or missing data from API responses.

The Problem

This code demonstrates the issue:

Javascript Error 
const user = undefined;
console.log(user.name); // Cannot read property

const data = {};
console.log(data.user.profile); // Nested access fails

The Solution

Here's the corrected code:

Javascript Fixed 
// Solution 1: Optional chaining (ES2020)
console.log(user?.name);
console.log(data?.user?.profile);

// Solution 2: Guard clauses
if (user && user.name) {
    console.log(user.name);
}

// Solution 3: Default objects
const safeUser = user || {};
console.log(safeUser.name);

Key Takeaways

Use optional chaining or proper checks for safe property access.