Logical Operator in JavaScript
In JavaScript, the logical operators are used to perform logical operations on values. The logical operators include logical AND (&&), logical OR (||), and logical NOT (!).
Types of Logical Operators in JavaScript​
The following are the types of logical operators in JavaScript:
Logical AND (&&)​
The logical AND (&&) operator returns true if both operands are true, otherwise it returns false.
let a = true;
let b = false;
console.log(a && b); // Output: false
Logical OR (||)​
The logical OR (||) operator returns true if at least one of the operands is true, otherwise it returns false.
let a = true;
let b = false;
console.log(a || b); // Output: true
Logical NOT (!)​
The logical NOT (!) operator returns true if the operand is false, and returns false if the operand is true.
let a = true;
console.log(!a); // Output: false
In the above examples, the logical AND (&&) operator returns false because the second operand is false. The logical OR (||) operator returns true because the first operand is true. The logical NOT (!) operator returns false because the operand is true.
Precedence of Logical Operators​
The logical AND (&&) operator has higher precedence than the logical OR (||) operator. The logical NOT (!) operator has the highest precedence.
You can use parentheses to change the order of evaluation of logical operators.
let a = true;
let b = false;
let c = true;
console.log(a || b && c); // Output: true
console.log((a || b) && c); // Output: true
1. Understanding Truthy and Falsy Values: In JavaScript, every value is either truthy or falsy. The logical operators return the value of the operand that determined the result, rather than true or false. You can use the logical operators to check for truthy or falsy values.
2. Handling Nullish Values: The logical operators can be used to handle nullish values. The logical OR (||) operator returns the first truthy operand, otherwise it returns the last operand. The logical AND (&&) operator returns the first falsy operand, otherwise it returns the last operand.
3. Logical Operators with Non-Boolean Values: The logical operators can be used with non-boolean values. The logical NOT (!) operator converts the operand to a boolean value and negates it. The logical AND (&&) and logical OR (||) operators return the value of the operand that determined the result.
4. Logical Operators with Multiple Operands: The logical operators can be used with multiple operands. The logical AND (&&) operator returns the first falsy operand, otherwise it returns the last operand. The logical OR (||) operator returns the first truthy operand, otherwise it returns the last operand.
5. Logical Operators with Side Effects: The logical operators can be used with expressions that have side effects. The logical AND (&&) operator returns the first operand if it is falsy, otherwise it returns the second operand. The logical OR (||) operator returns the first operand if it is truthy, otherwise it returns the second operand.
Conclusion​
In JavaScript, the logical operators are used to perform logical operations on values. The logical operators include logical AND (&&), logical OR (||), and logical NOT (!). The logical AND (&&) operator returns true if both operands are true, otherwise it returns false. The logical OR (||) operator returns true if at least one of the operands is true, otherwise it returns false. The logical NOT (!) operator returns true if the operand is false, and returns false if the operand is true.