Booleans

true or false
There are other data types that can yield true or false values on comparison
True: true, 1, 'Hello'
False: false, 0, ''

Operators

// Logical Operators      &&, ||, !
// Comparison Operators   >, >=, <, <=, ==, ===, !=, !== 

Double Equals vs. Triple Equals

('3' == 3 )    // True, because JS interpreter converts the string into a number.
('3' === 3 )   // False, type comparison is included.
(' ' == 0 )    // True.
(' ' === 0 )   // False.
( 'Ruby' < 'Python' )   // False. P comes before R in the alphabet.

If – Else If – Else

if ( condition ) {
  //code block 1
} else if ( condition ){
  //code block 2
} else {
  //code block 3
}