Operatori Aritmetici

Addizione (+)

L'operazione di addizione produce la somma di operandi numerici o la concatenzione di stringhe.

Sintassi

Operator: x + y

Esempi

// Numero + Numero -> addizione
1 + 2 // 3

// Booleano + Numero -> addizione
true + 1 // 2

// Booleano + Booleano -> additione
false + false // 0

// Numero + Stringa -> concatenazione
5 + "foo" // "5foo"

// Stringa + Booleano -> concatenazione
"foo" + false // "foofalse"

// Stringa + Stringa -> concatenazione
"foo" + "bar" // "foobar"

Sottrazione (-)

L'operatore di sottrazione fa la sottrazione dei due operandi e produce la loro differenza.

Sintassi

Operator: x - y

Esempi

5 - 3 // 2
3 - 5 // -2
"foo" - 3 // NaN

Divisione (/)

L'operatore di divisione produce il quoziente dei suoi operandi dove l'operando di sinistra è il dividendo e l'operando di destra è il divisore.

Sintassi

Operator: x / y

Esempi

1 / 2      // ritorna 0.5 in JavaScript
1 / 2      // ritorna 0 in Java 
// (nessuno degli operandi è un numero in virgola mobile esplicito)

1.0 / 2.0  // returns 0.5 in both JavaScript and Java

2.0 / 0    // returns Infinity in JavaScript
2.0 / 0.0  // returns Infinity too
2.0 / -0.0 // returns -Infinity in JavaScript

Moltiplicazione (*)

The multiplication operator produces the product of the operands.

Syntax

Operator: x * y

Examples

2 * 2 // 4
-2 * 2 // -4
Infinity * 0 // NaN
Infinity * Infinity // Infinity
"foo" * 2 // NaN

Modulo (%)

L'operatore modulo restituisce il resto rimasto quando un operando viene diviso per un secondo operando. It always takes the sign of the dividend, not the divisor. It uses a built-in modulo function to produce the result, which is the integer remainder of dividing var1 by var2 — for example — var1 modulo var2. There is a proposal to get an actual modulo operator in a future version of ECMAScript, the difference being that the modulo operator result would take the sign of the divisor, not the dividend.

Syntax

Operator: var1 % var2

Examples

12 % 5 // 2
-1 % 2 // -1
NaN % 2 // NaN
1 % 2 // 1
2 % 3 // 2
-4 % 2 // -0

Exponentiation (**)

The exponentiation operator returns the result of raising first operand to the power second operand. that is, var1var2, in the preceding statement, where var1 and var2 are variables. Exponentiation operator is right associative. a ** b ** c is equal to a ** (b ** c).

Syntax

Operator: var1 ** var2

Notes

In most languages like PHP and Python and others that have an exponentiation operator (typically ^ or **), the exponentiation operator is defined to have a higher precedence than other unary operators such as unary + and unary -, but there are a few exceptions. For example, in Bash or in the current ES2016 exponentiation operator draft spec, the ** operator is defined to have a lower precedence than unary operators.

-2 ** 2 // equals 4 in ES2016 or in Bash, equals -4 in other languages.

Examples

2 ** 3 // 8
3 ** 2 // 9
3 ** 2.5 // 15.588457268119896
10 ** -1 // 0.1
NaN ** 2 // NaN

2 ** 3 ** 2 // 512
2 ** (3 ** 2) // 512
(2 ** 3) ** 2 // 64

Increment (++)

The increment operator increments (adds one to) its operand and returns a value.

• If used postfix, with operator after operand (for example, x++), then it returns the value before incrementing.
• If used prefix with operator before operand (for example, ++x), then it returns the value after incrementing.

Syntax

Operator: x++ or ++x

Examples

// Postfix 
var x = 3;
y = x++; // y = 3, x = 4

// Prefix
var a = 2;
b = ++a; // a = 3, b = 3

Decrement (--)

The decrement operator decrements (subtracts one from) its operand and returns a value.

• If used postfix (for example, x--), then it returns the value before decrementing.
• If used prefix (for example, --x), then it returns the value after decrementing.

Syntax

Operator: x-- or --x

Examples

// Postfix 
var x = 3;
y = x--; // y = 3, x = 2

// Prefix
var a = 2;
b = --a; // a = 1, b = 1

Unary negation (-)

The unary negation operator precedes its operand and negates it.

Syntax

Operator: -x

Examples

var x = 3;
y = -x; // y = -3, x = 3

Unary plus (+)

The unary plus operator precedes its operand and evaluates to its operand but attempts to converts it into a number, if it isn't already. Although unary negation (-) also can convert non-numbers, unary plus is the fastest and preferred way of converting something into a number, because it does not perform any other operations on the number. It can convert string representations of integers and floats, as well as the non-string values true, false, and null. Integers in both decimal and hexadecimal ("0x"-prefixed) formats are supported. Negative numbers are supported (though not for hex). If it cannot parse a particular value, it will evaluate to NaN.

Syntax

Operator: +x

Examples

+3     // 3
+"3"   // 3
+true  // 1
+false // 0
+null  // 0

Specifications

Browser compatibility

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See also

• Assignment operators