JavaScript Operators: The Basics You Need to Know

Operators are the symbols that make things happen. Addition, comparison, logic — they power every piece of JavaScript you'll write. Here's what you need to know.

Arithmetic Operators

These do math. You've seen them before:

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);   // 3.333... — division
console.log(a % b);   // 1  — modulus (remainder)

The modulus operator % returns what's left over after division. 10 % 3 is 1 because 3 goes into 10 three times with 1 remaining. This is useful for checking if a number is even or odd:

console.log(10 % 2 === 0);  // true — 10 is even
console.log(7 % 2 === 0);    // false — 7 is odd

Comparison Operators

Comparisons return true or false:

console.log(5 > 3);    // true  — greater than
console.log(5 < 3);    // false — less than
console.log(5 >= 5);   // true  — greater than or equal
console.log(5 <= 4);   // false — less than or equal

Now, here's the one that trips up beginners — the difference between == and ===.

console.log(5 == '5');   // true — values match after conversion
console.log(5 === '5');  // false — different types, strict comparison

== converts types before comparing. '5' becomes 5, so they match. === checks both value and type. Since '5' is a string and 5 is a number, they're not equal.

The safe rule: always use === unless you have a specific reason not to. Unexpected type coercion causes bugs that are hard to find.

The same pattern applies to != vs !==:

console.log(5 != '5');    // false — they coerce to same value
console.log(5 !== '5');   // true  — different types, so not equal

Logical Operators

Logic operators let you combine conditions:

console.log(true && true);   // true  — AND: both must be true
console.log(true && false);  // false

console.log(true || false);  // true  — OR: at least one must be true
console.log(false || false); // false

console.log(!true);          // false — NOT: flips the value
console.log(!false);         // true

A common pattern — checking if a value is in range:

const age = 25;
if (age >= 18 && age < 65) {
  console.log('Working age');
}

Another — using OR for defaults:

const username = name || 'Anonymous';

If name is falsy (empty string, null, undefined), it falls back to 'Anonymous'.

Assignment Operators

The basic assignment operator = assigns a value:

let x = 10;

Compound assignment operators combine assignment with an operation:

let x = 10;

x += 5;   // x = 15 — add and assign
x -= 3;   // x = 12 — subtract and assign
x *= 2;   // x = 24 — multiply and assign
x /= 4;   // x = 6  — divide and assign
x %= 4;   // x = 2  — modulo and assign

These are shorthand for writing x = x + 5. Readable and common.

Practice Assignment

Try these exercises:

1. Perform arithmetic operations on two numbers:

const a = 15;
const b = 4;

console.log(a + b);   // 19
console.log(a % b);   // 3

1. Compare using both == and ===:

console.log(10 == '10');   // true
console.log(10 === '10');  // false

1. Write a condition using logical operators:

const temperature = 22;
const isRaining = false;

if (temperature > 20 && !isRaining) {
  console.log('Good weather for a walk');
}

Wrapping Up

Operators are everywhere in JavaScript. Arithmetic for math, comparisons for conditions, logical operators for combining checks, and assignment for storing values. The syntax is straightforward — the key is knowing the difference between == and === and when to use compound assignment operators. Get these fundamentals solid and the rest of JavaScript becomes much easier to follow.