Javascript

Question 1

What is the purpose of variables?

Answer 1

Used to hold data for scripting

Question 2

How do you declare a variable?

Answer 2

Use the keyword var then the name you want to give to the variable

Question 3

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

Answer 3

with the “=” sign.

Question 4

What characters are allowed in variable names?

Answer 4

letters, numbers, _, $

Question 5

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

Answer 5

var Apple is different then var apple

Question 6

What is the purpose of a string?

Answer 6

Strings hold information in text form.

Question 7

What is the purpose of a number?

Answer 7

numbers hold information in numerical form.
Used for math

Question 8

What is the purpose of a boolean?

Answer 8

to declare if something is true or false. Used for conditionals
Allow us to make decisions in code.

Question 9

What does the = operator mean in JavaScript?

Answer 9

Is being assigned to

Question 10

How do you update the value of a variable?

Answer 10

write the name of the variable with a different value

Question 11

What is the difference between null and undefined?

Answer 11

null is purposeful emptiness. (declared by developer)
undefined is accidental emptiness. (declared by javascript)

Question 12

Why is it a good habit to include “labels” when you log values to the browser console?

Answer 12

Helps with debugging.

Question 13

Give five examples of JavaScript primitives.

Answer 13

string, number, boolean, null, undefined

Question 14

What data type is returned by an arithmetic operation?

Answer 14

number

Question 15

What is string concatenation?

Answer 15

To join 2 or more strings together.

Question 16

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

Answer 16

can be used for arithmetic expressions and also string concatenation.

Question 17

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

Answer 17

boolean

Question 18

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

Answer 18

adds the value and assigns that result to original value.
ex: x+=y // x = x + y

Question 19

What are objects used for?

Answer 19

to store data with multiple properties(pieces of data) in a variable.

Question 20

What are object properties?

Answer 20

individual piece of named data within an object.

Question 21

Describe object literal notation.

Answer 21

declare the variable name it, “{
and key: value,
key: value,
};
object, key, value

Question 22

How do you remove a property from an object?

Answer 22

use the delete keyword followed by the object name and property name
delete object.property;

Question 23

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

Answer 23

object.property = ‘updated value’
object[‘property’] = ‘updated value’
dot notation and square bracket notation.

Question 24

What are arrays used for?

Answer 24

It is used to store a list of information/values.

Question 25

Describe array literal notation.

Answer 25

array = [ 'one', 'two', 'three'];

Question 26

How are arrays different from "plain" objects?

Answer 26

Values of an array are almost always the exact same data type. Has a length property as default.

Question 27

What number represents the first index of an array?

Answer 27

[0]

Question 28

What is the length property of an array?

Answer 28

shows total number of values are in the array.

Question 29

How do you calculate the last index of an array?

Answer 29

array.length - 1

Question 30

What is a function in JavaScript?

Answer 30

A process or set of actions with a name that can be reused within your code.

Question 31

Describe the parts of a function definition.

Answer 31

(function keyword) ->function nameOfFunction(parameter) { function block ends with return statement };

Question 32

Describe the parts of a function call.

Answer 32

nameOfFunction(argument); <-- argument is optional depending.

Question 33

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

Answer 33

function definitions include a function keyword and code block.

Question 34

What is the difference between a parameter and an argument?

Answer 34

parameter is used as a placeholder to define function, argument is the actual value used when you call it.

Question 35

Why are function parameters useful?

Answer 35

It gives you the ability to apply the function to many different things without writing a different function.

Question 36

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

Answer 36

1. return causes the function to produce a value. 2. Prevents any more code in the function code block from running.

Question 37

Why do we log things to the console?

Answer 37

To help with troubleshooting, to check your code.

Question 38

What is a method?

Answer 38

It is a function stored as a property of an object.

Question 39

How is a method different from any other function?

Answer 39

It has a dot notation.

Question 40

How do you remove the last element from an array?

Answer 40

Using the pop() method

Question 41

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

Answer 41

Math.floor() method

Question 42

How do you generate a random number?

Answer 42

Math.random() method

Question 43

How do you delete an element from an array?

Answer 43

splice() method splice(start, delete)

Question 44

How do you append an element to an array?

Answer 44

push() method

Question 45

How do you break a string up into an array?

Answer 45

split() method

Question 46

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

Answer 46

They do not, use console.log method on original string to verify

Question 47

Is the return value of a function or method useful in every situation?

Answer 47

No

Question 48

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

Answer 48

MDN

Question 49

Give 6 examples of comparison operators.

Answer 49

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

Question 50

What data type do comparison expressions evaluate to?

Answer 50

Boolean

Question 51

What is the purpose of an if statement?

Answer 51

Evaluate a condition to return a boolean and run instructions based on the boolean. It allows us to make decisions in our code.

Question 52

Is else statement required in order to use an if statement?

Answer 52

No

Question 53

Describe the syntax (structure) of an if statement.

Answer 53

if { is true { do this } }

Question 54

What are the three logical operators?

Answer 54

"&& || ! (and, or, not)"

Question 55

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

Answer 55

"use && ||"

Question 56

What is the purpose of a loop?

Answer 56

Loops allow an easy way to do something over and over.

Question 57

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

Answer 57

Condition's ultimate goal is to check if the loop should move forward. Ultimate goal is to stop the loop.

Question 58

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

Answer 58

A single repetition of the code block.

Question 59

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

Answer 59

Evaluated before each loop iteration. (iteration of the code block)

Question 60

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

Answer 60

Declared before the loop begins. Only runs one time.

Question 61

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

Answer 61

Evaluated before each loop iteration.

Question 62

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

Answer 62

After each iteration and before the condition

Question 63

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

Answer 63

break

Question 64

What does the ++ increment operator do?

Answer 64

adds +1 to the value permanently.

Question 65

How do you iterate through the keys of an object?

Answer 65

Use for for in loop.