Operators

Operators are the punctuation marks of the language: they take one or more values and produce a new one. JavaScript has dozens of them; in this lesson we look at the three most common families — arithmetic, comparison, logical — and learn to read their precedence.

Arithmetic

2 + 3; // 5
10 - 4; // 6
6 * 7; // 42
20 / 4; // 5
17 % 5; // 2   ← resto della divisione (modulo)
2 ** 10; // 1024 ← elevamento a potenza

The % operator (modulo) returns the remainder of integer division and is extremely useful: you'll use it to check whether a number is even (n % 2 === 0), to rotate indices, to format times.

Precedence and parentheses

As in math, * and / have higher precedence than + and -. When the calculation is not obvious, use parentheses: they make the intent explicit and protect you from bugs:

2 + 3 * 4; // 14   ← prima il prodotto
(2 + 3) * 4; // 20   ← prima la somma, grazie alle parentesi

Comparison

3 === 3; // true
3 === '3'; // false ← stesso "valore", tipi diversi
3 !== '3'; // true
5 > 3; // true
5 >= 5; // true

Logical

true && false; // false   ← AND: vero solo se entrambi sono veri
true || false; // true    ← OR: vero se almeno uno è vero
!true; // false   ← NOT: inverte

Both && and || are short-circuit: they stop evaluating as soon as the result is determined. This property is the basis for patterns like:

const nome = utente?.nome || 'Anonimo';
// se utente.nome è "falsy", usa 'Anonimo'

Try it

Review exercise