Contitional Property

JavaScript if
Use the JavaScript if statement to execute a block of code when a condition is true.

if (hour < 18) {
  greeting = "Good day";
}

Nested if
You can use an if statement inside another if statement:

let age = 16;
let country = "USA";
let text = "You can Not drive!";

if (country == "USA") {
  if (age >= 16) {
    text = "You can drive!";
  }
}

The else Statement
Use the else statement to specify a block of code to be executed if a condition is false.

JavaScript Ternary Operator
The conditional operator is a shorthand for writing conditional if...else statements.

It is called a ternary operator because it takes three operands.

let text = (age < 18) ? "Minor" : "Adult";

JavaScript Switch Statement
switch is often used as a more readable alternative to many if...else if...else statements, especially when dealing with multiple possible values.

switch (new Date().getDay()) {
  case 0:
    day = "Sunday";
    break;
  case 1:
    day = "Monday";
    break;
  case 2:
     day = "Tuesday";
    break;
  case 3:
    day = "Wednesday";
    break;
}

When JavaScript reaches a break keyword, it breaks out of the switch block.
This will stop the execution inside the switch block.

The default Keyword
The default keyword specifies a block of code to run if there is no case match.

JavaScript Booleans
In JavaScript, a Boolean is a primitive data type that can only have one of two values:

true or false

The Boolean value of an expression is the basis for all JavaScript comparisons and conditions.