JavaScript logical operation result

Examples of expressions that can be converted to false are those that evaluate to null, 0, the empty string (""), or undefined.

The following code shows examples of the && (logical AND) operator.

a1=true && true // t && t returns true
a2=true && false // t && f returns false
a3=false && true // f && t returns false
a4=false && (3 == 4) // f && f returns false
a5="Cat" && "Dog" // t && t returns Dog
a6=false && "Cat" // f && t returns false
a7="Cat" && false // t && f returns false

The following code shows examples of the || (logical OR) operator.

o1=true || true // t || t returns true
o2=false || true // f || t returns true
o3=true || false // t || f returns true
o4=false || (3 == 4) // f || f returns false
o5="Cat" || "Dog" // t || t returns Cat
o6=false || "Cat" // f || t returns Cat
o7="Cat" || false // t || f returns Cat