&& and || Operators

The comparison operators && (and) and || (or) test the boolean values of two or more expressions.

The && operator returns true if both sides are true.

true && true; // true

In the example above, true and true are referred to as the operands and && is the operator. Both operands return true, so the expression returns true.

If one or both of the operands is false, the && operator will return false.

false && true; // false
true && false; // false
false && false; // false

Here is how the && operator can be used in an if statement.

var age = 17;
if (age > 12 && age < 20) {
  console.log("This person is a teenager");
}

The variable age is set to 17, so both age > 12 and age < 20 evaluate to true. The string "This person is a teenager" is printed to the console.

The || operator returns true if one or both of the operands is true.

false || true; // true
true || false; // true
true || true; // true

The || operator returns false only if both of the operands are false.

false || false; // false

Here is how the || operator can be used in an if statement.

var age = 7;
if (age < 13 || age > 19) {
  console.log("This person is NOT a teenager");
}

The if statement will print "This person is NOT a teenager" to the console if the age is less than 13 or greater than 19.

console.log(true && false);

console.log(true || false);

console.log(true && true);

console.log(false || false);