Operators

You use operators constantly in JavaScript — every calculation, every comparison, every condition relies on them.

Arithmetic Operators

These perform math on numbers:

const a = 10;
const b = 3;

console.log(a + b);   // 13  — addition
console.log(a - b);   // 7   — subtraction
console.log(a * b);   // 30  — multiplication
console.log(a / b);   // 3.33... — division
console.log(a % b);   // 1   — remainder (modulo)
console.log(a ** b);  // 1000 — exponent (10³)

The modulo operator (%) gives the remainder after division. It's very useful for checking if a number is even or odd:

console.log(10 % 2);   // 0 — even
console.log(7 % 2);    // 1 — odd

Increment and Decrement

These shortcuts add or subtract 1 from a variable:

let count = 0;
count++;   // count is now 1
count++;   // count is now 2
count--;   // count is now 1

// Same as:
count = count + 1;

Assignment Operators

Assignment operators update a variable's value in one step:

let score = 10;

score += 5;   // score = score + 5  → 15
score -= 3;   // score = score - 3  → 12
score *= 2;   // score = score * 2  → 24
score /= 4;   // score = score / 4  → 6
score **= 2;  // score = score ** 2 → 36

Comparison Operators

Comparison operators compare two values and return true or false:

console.log(5 > 3);    // true
console.log(5 < 3);    // false
console.log(5 >= 5);   // true
console.log(5 <= 4);   // false
console.log(5 === 5);  // true  — strict equal (checks value AND type)
console.log(5 !== 3);  // true  — strict not equal

Logical Operators

Logical operators combine multiple conditions:

const age = 20;
const hasTicket = true;

// && (AND) — both must be true
console.log(age >= 18 && hasTicket);   // true

// || (OR) — at least one must be true
console.log(age < 18 || hasTicket);    // true

// ! (NOT) — flips true to false, and vice versa
console.log(!hasTicket);               // false

A practical example — checking if someone can enter:

const age = 20;
const hasID = true;

if (age >= 18 && hasID) {
  console.log("Welcome in!");
} else {
  console.log("Sorry, you can't enter.");
}

String Concatenation

The + operator joins strings together:

const first = "Coding";
const second = "Banana";

console.log(first + second);       // "CodingBanana"
console.log(first + " " + second); // "Coding Banana"

But mixing types can cause surprises:

console.log("5" + 3);    // "53"  — number is converted to string
console.log("5" - 3);    // 2     — string is converted to number
console.log(true + 1);   // 2     — true is treated as 1

Try It Yourself