The JavaScript tries to access data before the wire or API response is available.

Problem Explanation

LWCs render before async data arrives. Accessing nested fields without checks causes runtime errors.

Root Cause(s)

1. Missing null checks

2. Incorrect API response shape

3. Wire method not returning expected fields

Step-by-Step Solution

1. Use optional chaining (?.)

2. Guard rendering with if:true

3. Log the response structure in wiredResult

Edge Cases & Variations

1. Imperative Apex calls need manual loading states

2. Cacheable Apex may return stale data

Common Mistakes to Avoid

1. Assuming data exists on first render

2. Accessing nested objects blindly