Lesson 4: JavaScript Operators

Learning Objectives

By the end of this lesson, learners will:

• Understand what an operator is in programming
• Learn the different types of JavaScript operators
• Use arithmetic, assignment, comparison, and logical operators in code
• Know the difference between == and ===
• Write expressions that produce dynamic results

What Is an Operator?

In JavaScript, an operator is a symbol that performs an operation on one or more values (called operands). It tells the computer to do something, like add numbers, compare values, or assign variables.

📌 Example:

let total = 5 + 3; // "+" is an operator

1. Arithmetic Operators

Used to perform basic mathematical calculations.

📌 Example:

let a = 10;
let b = 3;

console.log(a % b); // 1 (remainder)
console.log(2 ** 4); // 16 (2 raised to the 4th power)

2. Assignment Operators

Used to assign values to variables.

📌 Example:

let x = 10;
x += 5; // same as x = x + 5
console.log(x); // 15

3. Comparison Operators

Used to compare values. These return Boolean results: true or false.

== vs ===: What’s the Difference?

• == checks only value and does type coercion
  → 5 == "5" → true
• === checks value and type (strict)
  → 5 === "5" → false

✅ Always use === in modern JavaScript to avoid unexpected results.

4. Logical Operators

Used to combine or invert Boolean expressions.

📌 Examples:

let isLoggedIn = true;
let isAdmin = false;

console.log(isLoggedIn && isAdmin); // false
console.log(isLoggedIn || isAdmin); // true
console.log(!isLoggedIn); // false

5. String Concatenation with +

The + operator is also used to combine strings.

📌 Example:

let firstName = "Alice";
let lastName = "Smith";
let fullName = firstName + " " + lastName;

console.log(fullName); // Alice Smith

🧠 If one operand is a string, + will treat the other as a string too.

6. Type Coercion

JavaScript tries to convert values automatically when needed.

📌 Example:

console.log("5" + 1); // "51" → number is converted to string
console.log("5" - 1); // 4 → string is converted to number

✅ Be careful — always use strict operators (===) to avoid confusion.

Practice Exercise

Try this in your browser console:

let a = 10;
let b = 5;

console.log(a + b);     // 15
console.log(a * b);     // 50
console.log(a == "10"); // true
console.log(a === "10"); // false
console.log(a > b && b < 3); // false

Summary Table