Comparison and Logical Operator

 

JavaScript Comparison and Logical 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

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.

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.

Strict Equal to Operator

const a = 2;

// strict equal operator

console.log(a === 2); // true

console.log(a === '2'); // false

• === evaluates to true 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.

Note: The difference between == and === is that:

• == evaluates to true if the operands are equal, however, === evaluates to true only if the operands are equal and of the same data type

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.

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.

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.

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.

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.

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.

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.

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.