Optional Chaining

optional chaining lets us write code where TypeScript can immediately stop running some expressions if we run into a null or undefined. We use the ?. operator for optional property accesses. When we write code like:

let x = foo?.bar.baz();

this is a way of saying that when foo is defined, foo.bar.baz() will be computed; but when foo is null or undefined, stop what we’re doing and just return undefined.

More plainly, that code snippet is the same as writing the following:

let x = foo === null || foo === undefined ? undefined : foo.bar.baz();