Quick Answer

Handle missing property errors.

Understanding the Issue

TypeScript enforces type shapes, preventing access to non-existent properties.

The Problem

This code demonstrates the issue:

Typescript Error 
interface User {
  name: string;
}
const user: User = { name: "John" };
console.log(user.age); // Error

The Solution

Here's the corrected code:

Typescript Fixed 
// Solution 1: Extend the interface
interface User {
  name: string;
  age?: number; // Optional property
}

// Solution 2: Type assertion (when certain)
console.log((user as any).age); // Not recommended

// Solution 3: Type guard
if ("age" in user) {
  console.log(user.age);
}

// Solution 4: Index signature
interface User {
  name: string;
  [key: string]: unknown;
}

Key Takeaways

Properly define types or use type guards for dynamic property access.