General - Beginning

Question 1

Name Three ways to define variables in JavaScript

Answer 1

var, let, const

Question 2

Give the definition of an “operator” in JavaScript.

Answer 2

An operator is a character or phrase that performs a task in our code.

typeof is an operator

(Arithmetic operators: + - * / %, etc)

Question 3

In a general sense, what is a “property” of a data type in JavaScript

Answer 3

Property in regards to data types would be information automatically generated about the data type in question.

Question 4

What is a method in JavaScript?

Answer 4

A method is a function that is a property of a Primitive Type or an Object.

Question 5

How do we invoke or call a method in JavaScript.

Answer 5

Methods are attached to their Primitive Type or Object with the dot operator (.) and Empty Parenthesis ().

Question 6

What are the 8 fundamental data types in JavaScript?

Answer 6

1. String
2. Number
3. Boolean
4. Null
5. Undefined
6. Symbol
7. BigInt
8. Object

Question 7

What is a mathematical assignment operator?

Answer 7

Mathematical assignment operators are built-in operators in javascript that help with incrementation. For example:

+=

-=

*=

/=

Question 8

What is the equivalent mathematical assignment operator to z = z + 1?

Answer 8

z += 1

Question 9

What is the z *= 2 equivalent to without using a mathematical assignment operator?

Answer 9

z = z * 2

Question 10

z = 5

z -= 1

z = ?

Answer 10

z = 4

Question 11

z = 6

z /= 2

z = ?

Answer 11

z = 3

Question 12

What is the increment operator in JavaScript and how is it used?

Answer 12

++

This mathematical assignment operator increase the value of something by 1

Question 13

What does the following represent and what is its function?

–

Answer 13

This is the decrement operator.

The decrement operator is a mathematical assignment operator that decreases the value of something by 1

Question 14

How can we check the type (data type) of a variable

Answer 14

We can use the ‘typeof’ operator in JavaScript.

console.log(typeof variableName)

Question 15

What are the two broad types of Methods in JavaScript.

Answer 15

Instance Methods - methods called on an object instance

Static Methods - methods called on an object constructor, not on an instance.

Question 16

What does it mean that JavaScript is weakly typed?

Answer 16

To be weakly typed means that we do not need to declare the type of data being stored in a variable.

Question 17

What is a conditional statement in JavaScript

Answer 17

A statement that checks a certain condition and performs an action based on that condition

Question 18

Give the syntax of an ‘if’ statement

Answer 18

if(condition){code block/block statement}

if condition evaluates to true, the code block will be executed

Question 19

Where would we use an if…else statement

Answer 19

When we have a binary decision that can evaluate to true or false

Question 20

What is the syntax of an else statement (assume the presence of an if statement)

Answer 20

else{code block/block statement}

when the if-statement evaluates to false the else code block will execute.

Question 21

List the comparison operators

Answer 21

1. < less than
2. > greater than
3. < = less than or equal to
4. > = greater than or equal to
5. === strictly equal to
6. ! == not strictly equal to

Question 22

What is the identity operator?

Answer 22

===

Question 23

What is the equality operator?

Answer 23

==

Question 24

How do the identity operator and equality operator differ

Answer 24

The equality operator ( == ) attempts to unify the data-types before comparison

The identity operator ( === ) will not attempt type conversion before comparison

Question 25

Name three logical operators

Answer 25

&& = and || = or ! = not

Question 26

How does the logical operator ‘or’ process a set of conditions?

Answer 26

The || operator evaluates the first conditional, if ‘true’ it does not check the second condition. If the first conditional is false, then the || operator checks the second condition

Question 27

How does the ‘not’ operator affect a condition?

Answer 27

The ! operator reverses the boolean value of a condition.

Question 28

Give examples of ‘falsy’ values

Answer 28

1. 0 2. ‘’ or “” 3. NaN 4. undefined 5. null

Question 29

How does the logical operator ‘and’ work?

Answer 29

The && operator evaluates both conditionals and if both are truthy returns the last conditional

Question 30

What is short circuit evaluation?

Answer 30

Short circuit evaluation uses logical operators to make code more concise (but potentially less legible).

Question 31

Given an example of using || in a short circuit evaluation.

Answer 31

let userName = ‘’ let welcome = userName || ‘Stranger’ will set welcome to ‘Stranger’ since userName is falsy.

Question 32

Give an example of short circuit evaluation using && operator.

Answer 32

hasFireworks && makeFestive() if hasFireworks is true then the makeFestive function will be called (because it is truthy).

Question 33

What is the ternary operator in JavaScript

Answer 33

? = ternary operator?

Question 34

How do we use the ternary operator?

Answer 34

The ternary operator can replace an if…else statement. [if statement] ? [ifTrueCode] : [ifFalseCode]

Question 35

What's the difference between a relative and absolute file path?

Answer 35

A relative path references the file based on the current directory An absolute path references the file based on the root or HTTP location

Question 36

How do you escape a character in JavaScript?

Answer 36

\ - backslash

Question 37

What is a JavaScript expression?

Answer 37

An expression is a valid set of literals, variables, operators, and expressions that evaluate to a single value.

Question 38

What is the assignment operator?

Answer 38

= - the equal sign, because it is used to assign something a value

Question 39

If an if or else…if statement evaluates to true does the code block continue to be read?

Answer 39

No, the code stops at the true conditional and exits the conditional flow.

Question 40

How is switch used for conditional evaluation?

Answer 40

switch can be used to replace multiple if, else…if, else conditionals.

Question 41

Give the syntax of a switch conditional statement.

Answer 41

switch(variableToExamine){ case 'condition1: do code break case 'condition2: do code break default: do code break }

Question 42

Will the switch conditional statement exit code upon a truthy result?

Answer 42

No, without a break statement following a conditional check, all other conditions will be evaluated.

Question 43

What is it called when JavaScript attempts type conversion on the comparison of values?

Answer 43

Casts or casting

Question 44

What is a common use case for the NOT operator?

Answer 44

It is often used to eliminate the else statement in a conditional. if(!variable){ do something if variable is empty}

Question 45

What does the value of undefined indicate?

Answer 45

Basically it indicates the lack of a value. We say something is undefined when it is not explicitly defined

Question 46

What does the value of null indicate?

Answer 46

Null indicates the intentional lack of a value. Developers need to intentionally set a value to null.

Question 47

How to null and undefined compare using strict equality comparison.

Answer 47

They are not equal because they are different primitives.

Question 48

What is scope in relation to variables?

Answer 48

Scope is the context in which our variables are declared and in which context they are available

Question 49

Where are variables in the global scope defined?

Answer 49

Things in the global scope are defined outside of function code blocks.

Question 50

Where are globally scoped variables able to be accessed?

Answer 50

Globally scoped variables can be accessed within any code block in the program.

Question 51

What is block scope in relation to variable declaration in JavaScript?

Answer 51

Block scope indicates that the variable is declared within a block of code.

Question 52

Where is a block scoped variable available

Answer 52

It is available within the block of code in which it is declared (basically within the curly braces)

Question 53

Where do globally defined variables ‘live’ in our code?

Answer 53

They reside in the ‘Global Namespace’

Question 54

What can too many variables in the Global Namespace cause and why is it undesirable?

Answer 54

They can cause Scope Pollution It is undesirable because it can be hard to keep track of many variables and there can be unexpected consequences of collisions an accidents.

Question 55

To avoid Scope Pollution what should we do with our variables?

Answer 55

We should scope them as tightly as possible.

Question 56

What are four benefits of tightly scoped variables?

Answer 56

1. Legibility 2. Clarity 3. Maintainability 4. Performant