JS Operators & Misc Grammar

Question 1

delete Operator

delete person.age;

Answer 1

deletes a property from an object

Question 2

in Operator

“firstName” in person
4 in array

Answer 2

returns true if the specified property is in the specified object, otherwise false

Question 3

instanceof Operator

cars instanceof Array

Answer 3

returns true if the specified object is an instance of the specified object

Question 4

break ?labelname;

use with label:
Loop2: 
    for (j = 10; j < 15; j++) {
        if (j === 12) {
            break Loop2;
        }
    }

Answer 4

exits a switch statement or a loop (for, for … in, while, do … while)

Question 5

continue ?labelname

Answer 5

breaks one iteration (in the loop) if a specified condition occurs, and continues with the next iteration in the loop

Question 6

debugger

Answer 6

enter debugging mode

Question 7

do…while

Answer 7

creates a loop that executes a block of code once, before checking if the condition is true, then it will repeat the loop as long as the condition is true

Question 8

for (statement 1; statement 2; statement 3) {
code block to be executed
}

Answer 8

creates a loop that is executed as long as a condition is true

Question 9

for (var in object) {
code block to be executed
}

for (x in person) {
text += person[x];
}

Answer 9

loops through the properties of an object.

The block of code inside the loop will be executed once for each property.

Question 10

return value;

Answer 10

stops the execution of a function and returns a value from that function

Question 11

switch(expression) {
    case n:
        code block
        break;
    case n:
        code block
        break;
    default:
        default code block
}

Answer 11

executes a block of code depending on different cases

Question 12

while (condition) {
code block to be executed
}

Answer 12

creates a loop that is executed while a specified condition is true

Question 13

Math.E

Answer 13

Returns Euler’s number (approx. 2.718)

Question 14

Math.LN2

Answer 14

Returns the natural logarithm of 2 (approx. 0.693)

Question 15

Math.LN10

Answer 15

Returns the natural logarithm of 10 (approx. 2.302)

Question 16

Math.LOG2E

Answer 16

Returns the base-2 logarithm of E (approx. 1.442)

Question 17

Math.LOG10E

Answer 17

Returns the base-10 logarithm of E (approx. 0.434)

Question 18

Math.PI

Answer 18

Returns PI (approx. 3.14)

Question 19

Math.SQRT1_2

Answer 19

Returns the square root of 1/2 (approx. 0.707)

Question 20

Math.SQRT2

Answer 20

Returns the square root of 2 (approx. 1.414)

Question 21

Math.abs(x)

Answer 21

Returns the absolute value of x

Question 22

Math.acos(x)

Answer 22

Returns the arccosine of x, in radians

Question 23

Math.asin(x)

Answer 23

Returns the arcsine of x, in radians

Question 24

Math.atan(x)

Answer 24

Returns the arctangent of x as a numeric value between -PI/2 and PI/2 radians

Question 25

Math.atan2(y,x)

Answer 25

Returns the arctangent of the quotient of its arguments

Question 26

Math.ceil(x)

Answer 26

Returns x, rounded upwards to the nearest integer

Question 27

Math.cos(x)

Answer 27

Returns the cosine of x (x is in radians)

Question 28

Math.exp(x)

Answer 28

Returns the value of E^x

Question 29

Math.floor(x)

Answer 29

Returns x, rounded downwards to the nearest integer

Question 30

Math.log(x)

Answer 30

Returns the natural logarithm (base E) of x

Question 31

Math.max(x,y,….)

Answer 31

Returns the number with the highest value

Question 32

Math.min(x,y,…)

Answer 32

Returns the number with the lowest value

Question 33

Math.pow(x,y)

Answer 33

Returns the value of x to the power of y

Question 34

Math.random()

Answer 34

Returns a random number between 0 and 1

Question 35

Math.round(x)

Answer 35

Rounds x to the nearest integer

Question 36

Math.sin(x)

Answer 36

Returns the sine of x (x is in radians)

Question 37

Math.sqrt(x)

Answer 37

Returns the square root of x

Question 38

Math.tan(x)

Answer 38

Returns the tangent of an angle