Null Value Problem

Why this happens

• A function returned null unexpectedly (e.g., querySelector found no element)

• A variable was explicitly set to null

• Missing data from an API response or database lookup

Minimal example

const user = null;
console.log(user.name);

const user = null;
console.log(user?.name);

How to diagnose

• Log the value before the line that fails to confirm it is null

• Trace where the null came from — which function or data source produced it

• Check API documentation for fields that may be null

How to fix

• Add a null check before using the value (if (value !== null))

• Use optional chaining (value?.property) to safely access properties

• Provide a fallback or default value when the value is null

How to prevent

• Always check for null before accessing properties on uncertain values

• Use optional chaining consistently in JavaScript and TypeScript

Related Resources