Operators II

Comparison operators

• == equal to
• != not equal to
• < less than
• > greater than
• <= less than or equal to
• >= greater than or equal to
• === equal to and same data type
• !== not equal to and/or different data types

Logical operators

• !a NOT: returns the opposite (true/false) of the operand
• a && b AND: returns true iff both operands are true
• a || b OR: returns true iff either operand is true

Bitwise operators

• a & b bitwise AND; returns 1 for each bit that is 1 in both operands
• a | b bitwise OR; returns 1 for each bit that is 1 in either operand
• a ^ b bitwise XOR; returns 1 for each bit that is 1 in only one operand
• ~a bitwise NOT; inverts bits of operand
• a << b shifts bits of a left by b bits (shifts in zeros)
• a >> b shifts bits of a right by b bits (propogates sign bit)
• a >>> b shifts bits of a right by b bits (shifts in zeros)

Boolean values in JavaScript

• false: false, 0, zero-length strings, null, undefined, NaN evaluate to false
• true: everything that isn't false evaluates to true
• !!(expr) helps "booleanize" an expression; many Boolean values in JavaScript won't equate even if they are both "truthy" or "falsey". A double not (!!) helps get most of the values into a more compatible state for comparisons. The parentheses are important for when a ! operator might take precedence over an operator in the expression and change its meaning.
• Special note: NaN is not equal to NaN