JavaScript Comparison and Logical Operators

JavaScript Comparison Operators

Comparison operators compare two values and give back a boolean value: either true or false. Comparison operators are used in decision making and loops.

Example 1: Equal to Operator

const a = 5, b = 2, c = 'hello';

// equal to operator
console.log(a == 5);     // true
console.log(b == '2');   // true
console.log(c == 'Hello');  // false

== evaluates to true if the operands are equal.

Note: In JavaScript, == is a comparison operator, whereas = is an assignment operator. If you mistakenly use = instead of ==, you might get unwanted result.

Example 2: Not Equal to Operator

const a = 3, b = 'hello';

// not equal operator
console.log(a != 2); // true
console.log(b != 'Hello'); // true

!= evaluates to true if the operands are not equal.

Example 3: Strict Equal to Operator

const a = 2;

// strict equal operator
console.log(a === 2); // true
console.log(a === '2'); // false

=== evaluates totrue if the operands are equal and of the same type. Here 2 and '2' are the same numbers but the data type is different. And === also checks for the data type while comparing.

Example 4: Strict Not Equal to Operator

 const a = 2, b = 'hello';

// strict not equal operator
console.log(a !== 2); // false
console.log(a !== '2'); // true
console.log(b !== 'Hello'); // true

!== evaluates to true if the operands are strictly not equal. It's the complete opposite of strictly equal ===.

In the above example, 2 !== '2' gives true. It's because their types are different even though they have the same value.

Example 5: Greater than Operator

const a = 3;

// greater than operator
console.log(a > 2); // true

> evaluates to true if the left operand is greater than the right operand.

Example 6: Greater than or Equal to Operator

const a = 3;

// greater than or equal operator
console.log(a >= 3); //true

>= evaluates to true if the left operand is greater than or equal to the right operand.

Example 7: Less than Operator

const a = 3, b = 2;

// less than operator
console.log(a < 2); // false
console.log(b < 3); // true

< evaluates to true if the left operand is less than the right operand.

Example 8: Less than or Equal to Operator

const a = 2;

// less than or equal operator
console.log(a <= 3) // true
console.log(a <= 2); // true

<= evaluates to true if the left operand is less than or equal to the right operand.

JavaScript Logical Operators

Logical operators perform logical operations: AND, OR and NOT.

Example 9: Logical AND Operator

const a = true, b = false;
const c = 4;

// logical AND
console.log(a && a); // true
console.log(a && b);  // false

console.log((c > 2) && (c < 2)); // false

&& evaluates to true if both the operands are true, else evaluates to false.

Note: You can also use logical operators with numbers. In JavaScript, 0 is false and all non-zero values are true.

Example 10: Logical OR Operator

const a = true, b = false, c = 4;


// logical OR
console.log(a || b); // true
console.log(b || b); // false
console.log((c>2) || (c<2)); // true

|| evaluates to true if either of the operands is true. If both operands are false, the result is false.

Example 11: Logical NOT Operator

const a = true, b = false;

// logical NOT
console.log(!a); // false
console.log(!b); // true

! evaluates to true if the operand is false and vice-versa.