Optional chaining '?.'

Question 1

let user = {};
alert(user.address.street);
// Error!

what to use then rewrite code:
alert( )

Answer 1

Optional chaining

alert( user?.address?.street ); // undefined (no error)

Question 2

let user = null;
let x = 0;

user?.sayHi(x++); // returns?

alert(x); // returns?

Answer 2

no “user”, so the execution doesn’t reach

0, value not incremented

Question 3

let user = null;

user?.name = “John”; // returns and why?

Answer 3

Error, doesn’t work because it evaluates to: undefined = “John”

Question 4

The optional chaining ?. has no use on the______

Answer 4

left side of an assignment.

Question 5

obj?.prop – returns //?

Answer 5

obj.prop if obj exists, otherwise undefined.

Question 6

obj?.[prop] – returns // ?

Answer 6

obj[prop] if obj exists, otherwise undefined.

Question 7

obj.method?.() – // returns?

Answer 7

calls obj.method() if obj.method exists, otherwise returns undefined.