How do I check for null and undefined in JavaScript?

How do I check if a variable is null or undefined in JavaScript?

You can use the strict equality operator (===) to check for null and undefined. For example: if (variable === null || variable === undefined) { ... }.

Is there a shorter way to check for both?

Yes! You can use the loose equality operator (==) which checks for both null and undefined: if (variable == null) { ... }.

What about using typeof?

You can use typeof variable === 'undefined' to check if a variable is undefined, but it won't check for null.

Can I use optional chaining to avoid these checks?

Yes, optional chaining (?.) allows you to safely access deeply nested properties without having to check for null or undefined.