foundations

Question 1

alert( 5 % 2 );
alert( 8 % 3 );
alert( 8 % 4 );

Answer 1

// 1, the remainder of 5 divided by 2
// 2, the remainder of 8 divided by 3
// 0, the remainder of 8 divided by 4

Question 2

let x = 0.2 + 0.1;
returns?

Answer 2

0.300000004

Question 3

let x = 0.2 + 0.1
returns 0.300000004

How to solve this problem to return 0.3?

Answer 3

To solve the problem above, it helps to multiply and divide:

let x = (0.2 * 10 + 0.1 * 10) / 10;

Question 4

let x = “10”;
let y = “20”;
let z = x + y;

returns?

Answer 4

1020

Question 5

let x = 10;
let y = “20”;
let z = x + y;

returns?

Answer 5

1020
concatination

Question 6

let x = “10”;
let y = 20;
let z = x + y;

returns?

Answer 6

1020
concatenation

Question 7

let x = 10;
let y = 20;
let z = “The result is: “ + x + y;

returns?

Answer 7

1020

Question 8

let x = 10;
let y = 20;
let z = “30”;
let result = x + y + z;

returns

Answer 8

3030

Question 9

JavaScript will try to convert _____ to numbers in all numeric operations:

Answer 9

strings

Question 10

JavaScript will try to convert strings to _______ in all numeric operations:

Answer 10

numbers

Question 11

JavaScript will try to convert strings to numbers in all numeric operations:

True or false

Answer 11

true

Question 12

let x = “100”;
let y = “10”;
let z = x + y;
let z = x - y;
let z = x / y;
let z = x * y;

Answer 12

10010
90
10
1000

Question 13

let x = 100 / “Apple”;
returns?

Answer 13

NAN

Question 14

You can use the global JavaScript function_______ to find out if a value is a not a number:

Answer 14

isNaN()

Question 15

let x = NaN;
let y = 5;
let z = x + y;

z returns?

Answer 15

NAN

Question 16

let x = NaN;
let y = “5”;
let z = x + y;

z returns?

Answer 16

NaN5

Question 17

NaN is a _____:

Answer 17

Number

Question 18

typeof NaN returns _______:

Answer 18

Number

Question 19

Division by 0 (zero) also generates ___________:

Answer 19

Infinity

Question 20

let x = 2 / 0;
let y = -2 / 0;

Answer 20

infinity
-infinity

Question 21

Infinity is a _____:

Answer 21

number

Question 22

typeof Infinity returns ______.

Answer 22

number

Question 23

let x = 123;
let y = new Number(123);

x returns
y returns

Answer 23

number
object

Question 24

let x = 500;
let y = new Number(500);
x==y returns

Answer 24

true

Question 25

let x = 500;
let y = new Number(500);
x===y returns

Answer 25

false

Question 26

let x = new Number(500);
let y = new Number(500);

x==y returns?

Answer 26

false

Question 27

let x = new Number(500);
let y = new Number(500);

x===y returns?

Answer 27

false

Question 28

alert( 2 ** 2 );
alert( 2 ** 3 );
alert( 2 ** 4 );

Answer 28

// 2² = 4
// 2³ = 8
// 2⁴ = 16

Question 29

alert(‘1’ + 2 + 2);

Answer 29

// “122” and not “14”

Question 30

alert( 6 - ‘2’ );
alert( ‘6’ / ‘2’ );

Answer 30

// 4, converts ‘2’ to a number
// 3, converts both operands to numbers

Question 31

let x = 1;
alert( +x );

Answer 31

// 1

Question 32

et y = -2;
alert( +y );

Answer 32

// -2

Question 33

// Converts non-numbers
alert( +true );
alert( +”” );

Answer 33

// 1
// 0

Question 34

let apples = “2”;
let oranges = “3”;

alert( +apples + +oranges );

Answer 34

// both values converted to numbers before the binary plus

// 5

Question 35

let apples = “2”;
let oranges = “3”;

// both values converted to numbers before the binary plus
alert( +apples + +oranges ); // 5

write out the longer variant

Answer 35

// alert( Number(apples) + Number(oranges) ); // 5

Question 36

alert( Number(apples) + Number(oranges) ); // 5

write shorter version

Answer 36

alert( +apples + +oranges );

Question 37

let a = 1;
let b = 2;

let c = 3 - (a = b + 1);

alert( a );
alert( c );

Answer 37

// 3
// 0

Question 38

let a, b, c;

a = b = c = 2 + 2;

alert( a );
alert( b );
alert( c );

Answer 38

4
4
4

Question 39

let n = 2;
n = n + 5;
n = n * 2;

write out short version

Answer 39

n += 5; // now n = 7 (same as n = n + 5)
n *= 2; // now n = 14 (same as n = n * 2)

Question 40

let n = 2;

n *= 3 + 5;

alert( n );

Answer 40

// right part evaluated first, same as n *= 8

16

Question 41

let counter = 2;
counter++;
alert( counter ); // returns

Answer 41

3

Question 42

write shorter
let counter = counters + 1

Answer 42

counter++

Question 43

let counter = 1;
let a = ++counter;

alert(a); // returns

Answer 43

2

Question 44

let counter = 1;
let a = counter++;

alert(a); // returns

Answer 44

1

Question 45

let counter = 0;
counter++;
++counter;
alert( counter ); //

Answer 45

2

the lines above did the same

Question 46

let counter = 0;
alert( ++counter ); // returns

Answer 46

1

Question 47

let counter = 0;
alert( counter++ ); //

Answer 47

0

Question 48

let counter = 1;
alert( 2 * ++counter ); // returns

Answer 48

4

Question 49

let counter = 1;
alert( 2 * counter++ ); // returns

Answer 49

2

Question 50

let a = (1 + 2, 3 + 4);

alert( a ); //

Answer 50

7 (the result of 3 + 4)

Question 51

The comma operator allows us to evaluate several expressions, dividing them with a comma ,. Each of them is evaluated but only __________ one is returned.

Answer 51

the result of the last

Question 52

console.log(“” + 1 + 0);
returns?

Answer 52

10

Question 53

console.log(“” - 1 + 0);

Answer 53

-1