Conditional Statements

Question 1

What does if, else if and else statement mean?

Answer 1

if: gives a condition
else: gives the option if condition is not true
else if: gives additional options
Note: else must be the last option in a conditional statement

Question 2

What follows after if? What does the condition evaluate?

Answer 2

• parenthesis for arguments (arg-n…)
• if condition is true, code in block statement executes
• if not, it is ignored.

Question 3

What is { }? When is it used?

Answer 3

Initiates a block statement. Used after conditional statement to run block of code within brackets.

Question 4

What is binary decisions?

Answer 4

yes-or-no questions. A decision tree in programming

Question 5

What are comparison values?

Answer 5

• Less than: <
• Greater than: >
• Less than or equal to: <=
• Greater than or equal to: >=
• Is equal to: ===
• Is not equal to: !==

Question 6

‘apples’ === ‘oranges’

What will be the boolean output? Why?

Answer 6

false, strictly equal will compare data types and the content of the data types

Question 7

What are logical operators?

Answer 7

• The and operator ( && )
• the or operator ( || )
• the not operator, AKA bang operator ( ! )

Question 8

What is special about || operator?

Answer 8

Think of the operator as or in a statement. If either side of the statement is true, boolean output will be true
Note: If first statement is true, the second statement wont be checked.

Question 9

//evaluates to true
!0
!NaN
!null
!undefined
Why?

Answer 9

Since they are falsey

Question 10

! + [] 
is converted internally into
! + String([])
! + "" 
What is the output?

Answer 10

//it evaluates true because ! on empty string returns true
Note: + operator only works on string and numbers, when we perform a binary operation on an arry, then the array is converted to a string.

Question 11

What are falsy values? What is the boolean value if not falsy?

Answer 11

-0
-Empty strings like “” or ‘’
null which represent when there is no value at all
Note: space in string will still be falsy
-undefined which represent when a declared variable lacks a value
-NaN, or Not a Number
Note: If not falsy, value will be truthy

Question 12

What is the output?
let numberOfApples = 0;

if (numberOfApples){
   console.log('Let us eat apples!');
} else {
   console.log('No apples left!');
}

Answer 12

// Prints ‘No apples left!’

Question 13

What is a ternary operator?

What does it look like?

Answer 13

short-hand to simplify if...else statement using ( ? ) and ( : )
Ex)
let isNightTime = true;

if (isNightTime) {
  console.log('Turn on the lights!');
} else {
  console.log('Turn off the lights!');
}
with ternary operators:

isNightTime ? console.log('Turn on the lights!') : console.log('Turn off the lights!');
/* If the condition evaluates to true, the first expression executes.
If the condition evaluates to false, the second expression executes. */

Question 14

When is a switch statement best used for?

Answer 14

-When you have to write multiple else if statements
Ex)
let groceryItem = ‘papaya’;

switch (groceryItem) {
  case 'tomato':
    console.log('Tomatoes are $0.49');
    break;
  case 'lime':
    console.log('Limes are $1.49');
    break;
  case 'papaya':
    console.log('Papayas are $1.29');
    break;
  default:
    console.log('Invalid item');
    break;
}

Question 15

What does the keyword ( break ) do?

Answer 15

-to exit the block and not execute any more code or check any other cases inside the code block.
// Note: Without break keywords, the first matching case will run, but so will every subsequent case regardless of whether or not it matches—including the default
-At the end of each switch statement, there is a default statement. If none of the cases are true, then the code in the default statement will run.