JavaScript FreeCodeCamp

Question 1

// This is a comment

Answer 1

Single line comment

Question 2

/* This is a multi-line comment */

Answer 2

multiple line comment

Question 3

NaN

Answer 3

not a number

Question 4

sometimes referred to as floating point numbers or floats

Answer 4

decimal numbers

Question 5

myVar % 2 = 1

Answer 5

Checks to see if myVar is odd. 1 = odd, 0 = even

Question 6

var sampleStr = “Alan said, "Peter is learning Javascript".”;

Answer 6

use \ to signal that “ should appear inside the string

Question 7

\n

Answer 7

newline

Question 8

\t

Answer 8

tab

Question 9

\b

Answer 9

word boundary

Question 10

\f

Answer 10

form feed

Question 11

firstName.length

Answer 11

returns the number of characters in the string in firstName

Question 12

zero-based indexing

Answer 12

programming languages start counting at 0

Question 13

var lastLetter = firstName[firstName.length - 1];

Answer 13

returns the last character in the string firstName

Question 14

multi-dimensional array

Answer 14

[[“Bulls, 23], [“White Sox”, 45]]

Question 15

myArray[0] = 15;

Answer 15

arrays are mutable and entries can be changed freely

Question 16

myArray[3][0][1]

Answer 16

equals the #3 entry, #0 entry in that array, and #1 entry in that array

Question 17

myArray.push(4);

Answer 17

appends 4 to the end of the array

Question 18

myArray.pop();

Answer 18

removes the last element from an array and returns that element

Question 19

myArray.shift();

Answer 19

removes the first element from an array and returns it

Question 20

myArray.unshift(4);

Answer 20

adds element to the beginning of the array

Question 21

function testFun(param1, param2) { }

Answer 21

creates a reusable function that takes parameters (arguments)

Question 22

==

Answer 22

equality operator. Returns true if both values are equal.

Question 23

===

Answer 23

Strict equality operator. Will not perform data type conversion.

Question 24

typeof 3

Answer 24

returns “number”

Question 25

typeof “3”

Answer 25

returns “string”

Question 26

!=

Answer 26

Inequality operator. Returns true if values are not equal.

Question 27

!==

Answer 27

Strict Inequality operator. Will not convert data types.

Question 28

&&

Answer 28

Logical and operator. Returns true if both operands are true

Question 29

||

Answer 29

Logical or operator. Returns true if either of the operands are true.

Question 30

var myObj = { 
 prop1: "val1", 
 prop 2: "val2"
};

Answer 30

creates an object

Question 31

myObj.prop1

Answer 31

returns the value in prop1 in the object myObj

Question 32

myObj[“Space Name”]

Answer 32

returns the value in “Space Name” in the object myObj

Question 33

delete ourDog.bark;

Answer 33

removes “bark” property from object ourDog

Question 34

myObj.hasOwnProperty(“propName”);

Answer 34

Returns true if the object has the given property

Question 35

JSON

Answer 35

JavaScript Object Notation

Question 36

while (i < 5) {
ourArray.push(i);
i++;
}

Answer 36

while loop. Runs while a specified condition is true.

Question 37

for (initialization; condition; final expression) { }

Answer 37

a for loop that runs for a specified number of times

Question 38

var i = 0;
do {
  ourArray.push(i);
  i++;
} while (i < 5);

Answer 38

Do-while loop. Runs the code at least once before checking the condition to see if it continues.

Question 39

Math.random()

Answer 39

function that generates a random decimal number between 0 (inclusive) to 1 (exclusive)

Question 40

Math.floor(num)

Answer 40

function that rounds the number down to a whole number

Question 41

Math.floor(Math.random() * 20)

Answer 41

gives a whole number between 0 and 19

Question 42

Math.floor(Math.random() * (max - min + 1)) + min

Answer 42

returns a whole number between min and max, inclusive

Question 43

parseInt(“”)

Answer 43

function that parses a string and returns the corresponding integer

Question 44

parseInt(string, radix)

Answer 44

Parses the string and returns an integer. The radix specifies the base number of the string. The radix can be an integer between 2 and 36.

Question 45

condition ? statement-if-true : statement-if-false;

Answer 45

conditional operator. A one line if-else expression