JavaScript Tutorial for Beginners: Comparison and Logical Operators

Learn how to use comparison and logical operators in JavaScript to compare values and control the flow of your code. Covers the different comparison operators, such as ==, <, and >, and the different logical operators, such as &&, ||, and !.

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.

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 type

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.

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