The logical AND operator is && and is applied to two values:
var result = true && false;
Logical AND behaves as the following truth table:
| Operand 1 | Operand 2 | Result |
|---|---|---|
| true | true | true |
| true | false | false |
| false | true | false |
| false | false | false |
Logical AND can be used with any data types, not just Boolean values.
When either operand is not a primitive Boolean, logical AND does not always return a Boolean value.
It uses the following rules:
| first AND second | Result |
|---|---|
| the first operand is an object | the second operand is always returned. |
| the second operand is an object | the object is returned only if the first operand evaluates to true. |
| both operands are objects | the second operand is returned. |
| If either operand is null | null is returned. |
| If either operand is NaN | NaN is returned. |
| If either operand is undefined | undefined is returned. |
The logical AND operator is a short-circuited operation.
If the first operand determines the result, the second operand is never evaluated.
If the first operand is false, the result is false.