Is it (`?:`) typescript ternary operator

You can use ?? operator!

const test: string = null;

console.log(test ?? 'none');

This will print 'none' because test is null. If there is a value for test, it will print that. You can try that here playground typescript

The ? operator indicate that the property can be nullable / optional. It just means that the compilator will not throw an error if you do not implement this property in your implementation.