Conditional Logic in JavaScript

Question 1

What is Conditional Logic good for?

Answer 1

It’s good for executing a set of instructions in one scenario but to do something else in another.

Question 2

What does an If Statement check?

Answer 2

An if Statement will check if an expression evaluates to true, and if it does, a subsequent code block will be executed.

Question 3

What is a Code Block?

Answer 3

A Code Block is a group of statements contained in a pair of curly braces {}

Question 4

What is a Condition?

Answer 4

An Expression used by an If Statement to evaluate whether it’s TRUE or FALSE

Question 5

How is an If Statement Constructed?

Answer 5

if (condition) { // code block to be executed if condition is true
}

Question 6

What part of the if statement is wrapped in curly braces?

Answer 6

The code block to be executed

Question 7

What is a Boolean Context?

Answer 7

A Boolean Context is any situation where JavaScript uses a Condition to decide whether or not to execute a certain code

Question 8

What are the other values, aside from true, that will evaluate to true in a boolean context?

Answer 8

any string except an empty string, any number other than zero, objects and arrays.

Question 9

What are the truthy values?

Answer 9

true itself, any strings except an empty string, any number except zero, objects and arrays.

Question 10

What is the name for all values that are not truthy?

Answer 10

Falsy values.

Question 11

What will falsy values evaluate to in a boolean context?

Answer 11

False

Question 12

What are the 6 falsy values?

Answer 12

NaN, Null, Undefined, an empty string, 0, false.

Question 12

How many falsy values are there in JavaScript?

Answer 12

6

Question 13

What does an empty string look like?

Answer 13

” “

Question 14

What is Null Usually assigned to a variable for?

Answer 14

To convey the absence of data

Question 15

What can an If-Else Statement be thought of?

Answer 15

As a fork in the road in our code. If we can’t go down one path, we can go down another.

Question 16

Which code block is executed when the if condition evaluates to false?

Answer 16

The else code block will be executed.

Question 17

What happens if we chain if statements?

Answer 17

By chaining if statements, we can create as many forks in our code as we wish.

Question 18

What are Ternary Statements an alternative way of doing?

Answer 18

Ternary Statements are an alternative way of using an expression in a boolean context that can make code more concise in certain situations.

Question 19

Why would this code resolve to a Reference Error?
const isVirtualPetHappy = true;

if (isVirtualPetHappy) {
let action = ‘wag tail’
} else {
let action = ‘whimper’
};

console.log(action)

Answer 19

The code would resolve to a Reference Error because the action inside console.log(action) has been declared inside a code block {} which makes it unavailable later on in the code.

Question 20

How would you correct The Reference Error?

Answer 20

By Declaring the Variable before the If Statement but waiting to Initialise It.

Question 21

Why would this code correctly run instead?
const isVirtualPetHappy = true;
let action;

if (isVirtualPetHappy) {
action = ‘wag tail’
} else {
action = ‘whimper’
};

console.log(action)

Answer 21

The code will run because the variable (action) in console.log(action) has been declared before the if Statement but hasn’t been initialised =’wag tail’ or ‘whimper’ until after the if statement.

Question 22

Why are these two codes the equivalent of one another?
const action = isVirtualPetHappy ? ‘wag tail’ : ‘whimper’;
+
const isVirtualPetHappy = true;
let action;
if (isVirtualPetHappy) {
action = ‘wag tail’
} else {
action = ‘whimper’
};

console.log(action)

Answer 22

One is a Ternary Statement.

Question 23

What is the symbol used for the Ternary Statement?

Answer 23

?

Question 24

How does this code work? const action = isVirtualPetHappy ? 'wag tail' : 'whimper';

Answer 24

The constant variable is declared action and we assign the ternary operator by placing it's symbol (?) after the if statement. If the value of the if statement is truthy, then it will evaluate to the first expression 'wag tail'. If the value of the statement if falsy, then it will evaluate to the second expression 'whimper.'

Question 25

What 3 parts can a Ternary Statement be broken down into?

Answer 25

condition ? expressionIfTrue : expressionIfFalse

Question 26

What are Switch Statements?

Answer 26

Switch Statements allow us to execute code based on a set of conditions, known as cases.

Question 27

What is Switch Statements a Clearer Way of Doing?

Answer 27

Switch Statements are a clearer way of managing the flow of your code when you have several or more conditions.

Question 28

What does a Switch Statement start with?

Answer 28

Switch Statements start with the keyword switch followed by a set of parentheses () that wrap an expression.

Question 29

What follows the beginning of a Switch Statement?

Answer 29

It's followed by a code block containing cases - a set of conditions, one of which will match the expression.

Question 30

What is the break keyword used for in a Switch Statement?

Answer 30

Each case may contain code to execute or it may fall through to the next case and if these two scenarios are not desired then a break keyword is used at the end of each case to stop any more code in the switch statement from executing.

Question 31

What does it mean when the default case is executed?

Answer 31

The default cause is executed when none of the cases match.