Nullish coalescing operator '??'

Question 1

_____ returns the first argument if it’s not null/undefined. Otherwise, the second one.

Answer 1

//
nullish coalescing operator

Question 2

nullish coalescing operator returns?

Answer 2

first agrument if it’s not null or undefined

Question 3

let user;
alert(user ?? “Anonymous”); //
returns and why?

Answer 3

Anonymous
because user is undefined

Question 4

let user = “John”;
alert(user ?? “Anonymous”); //
returns and why?

Answer 4

John
(user is not null/undefined)

Question 5

let user = “John”;
alert(“Anonymous” ?? user);
// returns and why

Answer 5

undefined
first argument is “undefined”

Question 6

let firstName = null;
let lastName = null;
let nickName = “Supercoder”;

alert(firstName ?? lastName ?? nickName ?? “Anonymous”);
// returns and why

Answer 6

Supercoder
firstname and lastname is null

Question 7

?? returns the first ______ value

Answer 7

defined

Question 8

|| returns the first ______ value.

Answer 8

truthy

Question 9

let height = 0;
alert(height || 100);
// returns and why

Answer 9

100

The height || 100 checks height for being a falsy value, and it’s 0, falsy indeed.
so the result of || is the second argument, 100.

Question 10

let height = 0;
alert(height ?? 100);
// returns and why?

Answer 10

0

The height ?? 100 checks height for being null/undefined, and it’s not, so the result is height “as is”, that is 0

Question 11

The ______ provides a short way to choose the first “defined” value from a list.

Answer 11

nullish coalescing operator ??

Question 12

let x = 1 && 2 ?? 3;
// the above give a Syntax error how can you fix?

Answer 12

need parentheses