Arithmetic operators take numerical values (either literals or variables) as their operands and return a single numerical value. The standard arithmetic operators are addition (+), subtraction (-), multiplication (*), and division (/).
The addition operator produces the sum of numeric operands or string concatenation.
Operator: x + y
// Number + Number -> addition 1 + 2 // 3 // Boolean + Number -> addition true + 1 // 2 // Boolean + Boolean -> addition false + false // 0 // Number + String -> concatenation 5 + "foo" // "5foo" // String + Boolean -> concatenation "foo" + false // "foofalse" // String + String -> concatenation "foo" + "bar" // "foobar"
The subtraction operator subtracts the two operands, producing their difference.
Operator: x - y
5 - 3 // 2 3 - 5 // -2 "foo" - 3 // NaN
The division operator produces the quotient of its operands where the left operand is the dividend and the right operand is the divisor.
Operator: x / y
1 / 2 // returns 0.5 in JavaScript 1 / 2 // returns 0 in Java // (neither number is explicitly a floating point number) 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
The multiplication operator produces the product of the operands.
Operator: x * y
2 * 2 // 4 -2 * 2 // -4 Infinity * 0 // NaN Infinity * Infinity // Infinity "foo" * 2 // NaN
The remainder operator returns the first operand modulo the second operand, that is, var1
modulo var2
, in the preceding statement, where var1
and var2
are variables. The modulo function is the integer remainder of dividing var1
by var2
. There is a proposal to get an actual modulo operator in a future version of ECMAScript.
Operator: var1 % var2
12 % 5 // 2 -1 % 2 // -1 NaN % 2 // NaN 1 % 2 // 1 2 % 3 // 2 -4 % 2 // -0
[ECMAScript 2016 (ES7) proposal]
The exponentiation operator returns the result of raising first operand to the power second operand. that is, var1
var2
, in the preceding statement, where var1
and var2
are variables. Exponentiation operator is right associative. a ** b ** c
is equal to a ** (b ** c)
.
Operator: var1 ** var2
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 ES7 exponentiation operator draft spec, the ** operator is defined to have a lower precedence than unary operators.
-2 ** 2 // equals 4 in ES7 or in Bash, equals -4 in other languages.
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
The increment operator increments (adds one to) its operand and returns a value.
Operator: x++ or ++x
// Postfix var x = 3; y = x++; // y = 3, x = 4 // Prefix var a = 2; b = ++a; // a = 3, b = 3
The decrement operator decrements (subtracts one from) its operand and returns a value.
Operator: x-- or --x
// Postfix var x = 3; y = x--; // y = 3, x = 2 // Prefix var a = 2; b = --a; // a = 1, b = 1
The unary negation operator precedes its operand and negates it.
Operator: -x
var x = 3; y = -x; // y = -3, x = 3
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.
Operator: +x
+3 // 3 +"3" // 3 +true // 1 +false // 0 +null // 0
Created by Mozilla Contributors, license: CC-BY-SA 2.5