variables & datatypes

Question 1

Shorten the below

let user = ‘John’;
let age = 25;
let message = ‘Hello’;

Answer 1

let user = ‘John’, age = 25, message = ‘Hello’;

Question 2

let hello = ‘Hello world!’;
let message;
message = hello;

alert(hello); // returns?
alert(message); // returns?

Answer 2

Hello world!
Hello world!

Question 3

varibles cannot start with a _____ or have a _____

Answer 3

digit
hyphon

Question 4

reserved variable words

Answer 4

let, class, return, function

Question 5

Besides regular numbers, there are so-called “special numeric values” which also belong to this data type; name the 3

Answer 5

Infinity, -Infinity and NaN.

Question 6

alert( 1 / 0 ); // returns

Answer 6

infinity

Question 7

alert( “not a number” / 2 )

returns?

Answer 7

infinity

Question 8

alert( NaN + 1 ); // returns

Answer 8

NAN

Question 9

alert( 3 * NaN ); // returns

Answer 9

NAN

Question 10

alert( “not a number” / 2 - 1 )
// returns

Answer 10

NAN

Question 11

So, if there’s a NaN somewhere in a mathematical expression, it propagates to the whole result (there’s only one exception to that: )

Answer 11

NaN ** 0 is 1

Question 12

let name = “John”;

// embed a variable
alert( Hello, \_\_\_\_\_\_ ! ); // Hello, John!

Answer 12

${name}

Question 13

The expression inside ${…} is evaluated and the result becomes a part of the string but can only be done with ______.

Answer 13

backticks
``

Question 14

______ is just a special value which represents “nothing”, “empty” or “value unknown”.

Answer 14

NULL

Question 15

The meaning of ________ is “value is not assigned”.

Answer 15

undefined

Question 16

let age;
alert(age); // returns?

Answer 16

shows “undefined”

Question 17

typeof undefined //
returns?

Answer 17

“undefined”

Question 18

typeof 10n // returns?

Answer 18

“bigint”

Question 19

typeof null // returns?

Answer 19

“object”