Lesson 6: JavaScript Comparison Operators
Master JavaScript comparison operators with interactive examples and real-world applications.
6.1 Comparison Operators in JavaScript
Comparison operators allow you to compare values and determine the relationship between them. These operators return a boolean value (true or false) based on the comparison result.
Comparison Operators Table
Operator | Name | Description | Example |
---|---|---|---|
== | Equal to | Returns true if operands are equal | 5 == 5 → true |
!= | Not equal | Returns true if operands are not equal | 5 != 3 → true |
=== | Strict equal | Returns true if operands are equal and of same type | 5 === '5' → false |
!== | Strict not equal | Returns true if operands are not equal or not same type | 5 !== '5' → true |
> | Greater than | Returns true if left operand is greater than right | 10 > 5 → true |
< | Less than | Returns true if left operand is less than right | 10 < 5 → false |
>= | Greater than or equal | Returns true if left operand is greater than or equal to right | 10 >= 10 → true |
<= | Less than or equal | Returns true if left operand is less than or equal to right | 10 <= 5 → false |
Using if Statements
The if
keyword allows you to execute code conditionally:
if (condition) { // Code to execute if condition is true }
Example 6.1: Basic if Statement
let mark = window.prompt("Enter your mark:", "0"); if (mark >= 80) { document.write("Grade=A"); }
If the mark entered is 80 or more, the browser displays "Grade=A", otherwise nothing happens.
6.2 Interactive Comparison Demos
Try these interactive demos to see JavaScript comparison operators in action:
Number Comparison Demo
Compare Two Numbers
Grade Calculator
Equality Comparison
Understand the difference between ==
(loose equality) and ===
(strict equality):
Loose Equality (==)
Strict Equality (===)
6.3 Logical Operators
Logical operators allow you to combine multiple conditions:
Logical AND (&&)
Returns true if both conditions are true
if (age >= 18 && hasLicense) { // Can drive }
Logical OR (||)
Returns true if at least one condition is true
if (isStudent || isSenior) { // Apply discount }
Logical NOT (!)
Inverts the boolean value
if (!isRaining) { // Go outside }
Truth Tables
AND (&&) Truth Table
A | B | A && B |
---|---|---|
true | true | true |
true | false | false |
false | true | false |
false | false | false |
OR (||) Truth Table
A | B | A || B |
---|---|---|
true | true | true |
true | false | true |
false | true | true |
false | false | false |
NOT (!) Truth Table
A | !A |
---|---|
true | false |
false | true |
Logical Operators Demo
Entry Fee Calculator
Membership Check
6.4 Practical Applications
Comparison and logical operators are fundamental to many real-world applications. Here are practical examples:
Example 6.4: Form Validation
function validateForm() { const name = document.getElementById("name").value; const email = document.getElementById("email").value; const password = document.getElementById("password").value; const confirmPassword = document.getElementById("confirmPassword").value; // Validation checks if (name === "") { alert("Name is required!"); return false; } if (!email.includes("@")) { alert("Please enter a valid email address!"); return false; } if (password.length < 8) { alert("Password must be at least 8 characters!"); return false; } if (password !== confirmPassword) { alert("Passwords do not match!"); return false; } alert("Form submitted successfully!"); return true; }
Example 6.5: Access Control System
function checkAccess() { const age = parseInt(prompt("Enter your age:")); const hasMembership = confirm("Do you have a membership?"); const isWeekend = new Date().getDay() === 0 || new Date().getDay() === 6; if (age < 18) { alert("Access denied. You must be at least 18 years old."); } else if (hasMembership) { alert("Welcome, member! Enjoy your visit."); } else if (isWeekend) { alert("Weekend access is for members only. Please consider joining!"); } else { alert("Welcome! Regular admission applies."); } }