Basics

Operators

Arithmetic, comparison, logical, assignment and ternary operators.

1. Explanation

Operators combine or compare values. Arithmetic: + - * / % **. Comparison: === !== > < >= <=. Always prefer === (strict equality) over == (loose). Logical: && || !. Assignment: = += -= *=. Ternary: condition ? a : b. Nullish coalescing ?? returns the right side only when the left is null or undefined.

2. Example

Try it yourself

console.log(10 + 5);       // 15
console.log(10 % 3);       // 1   (remainder)
console.log(2 ** 8);       // 256 (power)
console.log(5 === "5");    // false (strict)
console.log(5 == "5");     // true  (loose — avoid)
console.log(true && "yes"); // "yes"
console.log(null ?? "fallback"); // "fallback"
const age = 20;
console.log(age >= 18 ? "Adult" : "Minor");

Console

Click Run to see output.

3. Expected output

output

15
1
256
false
true
yes
fallback
Adult

4. Common mistakes

✗Using == instead of === leads to surprising coercions
✗Confusing % (remainder) with division
✗Forgetting operator precedence: 2 + 3 * 4 is 14, not 20

5. Practice questions

Check if a number is divisible by 7
Use a ternary to print 'pass' or 'fail' for a score >= 40
Use ?? to provide a default for an undefined variable

→ Try more practice problems