javascript - How to use optional chaining with array or functions?

Question

I'm trying to use optional chaining with an array instead of an object but not sure how to do that:

Here's what I'm trying to do myArray.filter(x => x.testKey === myTestKey)?[0]. Also trying similar thing with a function:

let x = {a: () => {}, b: null}
console.log(x?b());

But it's giving an error like that so how to use it with an array or a function.

Answer 1

You need to put a . after the ? to use optional chaining:

myArray.filter(x => x.testKey === myTestKey)?.[0]

Playground link

Using just the ? alone makes the compiler think you're trying to use the conditional operator (and then it throws an error since it doesn't see a : later)

Optional chaining isn't just a TypeScript thing - it is a finished proposal in plain JavaScript too.

It can be used with bracket notation like above, but it can also be used with dot notation property access:

const obj = {
  prop2: {
    nested2: 'val2'
  }
};

console.log(
  obj.prop1?.nested1,
  obj.prop2?.nested2
);