JavaScript

Question 1

What is the purpose of variables?

Answer 1

A variable is a way to store values.

Question 2

How do you declare a variable?

Answer 2

Use the reserved keyword var to declare a variable in JavaScript. Syntax: var ; var = ; A variable must have a unique name.

Question 3

How do you initialize (assign a value to) a variable?

Answer 3

You can assign a value to a variable using the = operator when you declare it or after the declaration and before accessing it

Question 4

What characters are allowed in variable names?

Answer 4

Start them with a letter, underscore _, or dollar sign $.
After the first letter, you can use numbers, as well as letters, underscores, or dollar signs.
Don’t use any of JavaScript’s reserved keywords.

Question 5

What does it mean to say that variable names are “case sensitive”?

Answer 5

means that language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.

Question 6

What is the purpose of a string?

Answer 6

to represent text rather than numbers

Question 7

What is the purpose of a number?

Answer 7

to represent and manipulate numbers

Question 8

What is the purpose of a boolean?

Answer 8

to create true/false statements

Question 9

What does the = operator mean in JavaScript?

Answer 9

assigns a value to its left operand based on the value of its right operand.

Question 10

What is the difference between null and undefined

Answer 10

undefined is a type, whereas null an object

Question 11

Give five examples of JavaScript primitives.

Answer 11

undefined , null , boolean , string and number

Question 12

What data type is returned by an arithmetic operation?

Answer 12

numeric data

Question 13

What is string concatenation?

Answer 13

Concatenation is the process of appending one string to the end of another string

Question 14

What purpose(s) does the + plus operator serve in JavaScript?

Answer 14

precedes its operand and evaluates to its operand but attempts to convert it into a number, if it isn’t already

Question 15

What data type is returned by comparing two values (, ===, etc)?

Answer 15

boolean

Question 16

What does the += “plus-equals” operator do?

Answer 16

adds the value on the right, to the variable on the left, and then assigns that value back into the variable on the left.

Question 17

What is object used for?

Answer 17

An object is an abstract data type with the addition of polymorphism and inheritance.

Question 18

What are object properties?

Answer 18

Object properties are defined as a simple association between name and value

Question 19

Describe object literal notation.

Answer 19

The Object literal notation is basically an array of key:value pairs, with a colon separating the keys and values, and a comma after every key:value pair, except for the last, just like a regular array

Question 20

How do you remove a property from an object?

Answer 20

delete operator

Question 21

What are the two ways to get or update the value of a property?

Answer 21

dot notation and square brackets

Question 22

What are arrays used for?

Answer 22

to store a collection of data

Question 23

Describe array literal notation.

Answer 23

array literal notation is where you define a new array using just empty brackets.

Question 24

How are arrays different from “plain” objects?

Answer 24

object store different types of data, dont have orders. array store same types of data, have orders.

Question 25

What number represents the first index of an array?

Answer 25

0

Question 26

What is the length property of an array?

Answer 26

how many pieces in the array

Question 27

How do you calculate the last index of an array?

Answer 27

array.length-1

Question 28

What is a function in JavaScript?

Answer 28

a set of statements that performs a task or calculates a value

Question 29

Describe the parts of a function definition.

Answer 29

A function has three parts, a set of inputs, a set of outputs, and a rule that relates the elements of the set of inputs to the elements of the set of outputs in such a way that each input is assigned exactly one output.

Question 30

Describe the parts of a function call.

Answer 30

Function calls contain the name of the function being executed followed by a list of values, called arguments, which are assigned to the parameters in the function definition

Question 31

When comparing them side-by-side, what are the differences between a function call and a function definition?

Answer 31

A function is a piece of code which enhanced the reusability and modularity of your program. It means that piece of code need not be written again. A function call means invoking or calling that function. Unless a function is called there is no use of that function.

Question 32

What is the difference between a parameter and an argument?

Answer 32

The values that are declared within a function when the function is called are known as an argument. Whereas, the variables that are defined when the function is declared are known as a parameter.

Question 33

Why are function parameters useful?

Answer 33

Parameters allow us to pass information or instructions into functions and procedures .

Question 34

What two effects does a return statement have on the behavior of a function?

Answer 34

A return statement ends the execution of a function, and returns control to the calling function.

Question 35

Why do we log things to the console?

Answer 35

console. log specifically is a method for developers to write code to inconspicuously inform the developers what the code is doing

Question 36

What is a method?

Answer 36

A JavaScript method is a property of an object that contains a function definition.

Question 37

How is a method different from any other function?

Answer 37

a method is associated with an object, while a function is not

Question 38

How do you remove the last element from an array?

Answer 38

pop()

Question 39

How do you round a number down to the nearest integer?

Answer 39

floor()

Question 40

How do you generate a random number?

Answer 40

random()

Question 41

How do you delete an element from an array?

Answer 41

splice()

Question 42

How do you append an element to an array?

Answer 42

push() to the end; unshift() to the beginning

Question 43

How do you break a string up into an array?

Answer 43

split()

Question 44

Do string methods change the original string? How would you check if you weren't sure?

Answer 44

no, console.log origin string out

Question 45

What three-letter acronym should you always include in your Google search about a JavaScript method or CSS property

Answer 45

MDN

Question 46

Give 6 examples of comparison operators

Answer 46

>,=,<=,!=,===

Question 47

What data type do comparison expressions evaluate to?

Answer 47

bolean

Question 48

What is the purpose of an if statement?

Answer 48

The IF statement is a decision-making statement that guides a program to make decisions based on specified criteria

Question 49

Is else required in order to use an if statement?

Answer 49

else is compulsory to use with if statement.

Question 50

What are the three logical operators?

Answer 50

and , or, not

Question 51

How do you compare two different expressions in the same condition?

Answer 51

and or or

Question 52

What is the purpose of a loop?

Answer 52

Loops allow you to repeat a process over and over without having to write the same (potentially long) instructions each time you want your program to perform a task.

Question 53

What is the purpose of a condition expression in a loop?

Answer 53

tell loop when to stop

Question 54

What does "iteration" mean in the context of loops?

Answer 54

Iteration is the repetition of a process in a computer program, usually done with the help of loops.

Question 55

When does the condition expression of a while loop get evaluated?

Answer 55

before executing the statement.

Question 56

When does the initialization expression of a for loop get evaluated?

Answer 56

before the loop begin

Question 57

When does the condition expression of a for loop get evaluated?

Answer 57

at the end of each loop iteration

Question 58

When does the final expression of a for loop get evaluated?

Answer 58

at the end of the loop iteration

Question 59

Besides a return statement, which exits its entire function block, which keyword exits a loop before its condition expression evaluates to false?

Answer 59

break;

Question 60

How do you iterate through the keys of an object?

Answer 60

for in loop

Question 61

What is the className property of element objects

Answer 61

to set or return the value of an element's class attribute

Question 62

How do you update the CSS class attribute of an element using JavaScript

Answer 62

use queryselector to select the query then use className to change

Question 63

What is the textContent property of element objects?

Answer 63

The textContent property returns: The text content of the element and all descendaces, with spacing and CSS hidden text, but without tags

Question 64

How do you update the text within an element using JavaScript?

Answer 64

use queryselector to select the query then use textContent to change

Question 65

What is a client?

Answer 65

a desktop computer or workstation that is capable of obtaining information and applications from a server.

Question 66

what is a server

Answer 66

a server is a piece of computer hardware or software that provides functionality for other programs or devices, A server stores, sends, and receives data