Unable to read properties of undefined
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Unable to read properties of undefined
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:true3. Log the response structure in
wiredResultget accountName() {
return this.accountData?.Name;
}
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