The unary plus operator (+
) precedes its operand and evaluates to its operand but attempts to convert it into a number, if it isn't already.
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Syntax
Operator: +x
Description
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). Using the operator on BigInt values throws a TypeError. If it cannot parse a particular value, it will evaluate to NaN
.
Examples
Usage with numbers
const x = 1; const y = -1; console.log(+x); // 1 console.log(+y); // -1
Usage with non-numbers
+true // 1 +false // 0 +null // 0 +function(val){ return val } // NaN +1n // throws TypeError: Cannot convert BigInt value to number
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Unary plus operator' in that specification. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Unary plus (+ ) | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 3 | Opera Full support 4 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.1.100 |
Legend
- Full support
- Full support