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Unary plus (+)

The + operator precedes its operand and evaluates to its operand but attempts to convert it into a number, if it isn't already.

Try it

Syntax

js
+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.

Unary plus does the exact same steps as normal number coercion used by most built-in methods expecting numbers. 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. Unlike other arithmetic operators, which work with both numbers and BigInts, using the + operator on BigInt values throws a TypeError.

Examples

Usage with numbers

js
const x = 1;
const y = -1;

console.log(+x);
// 1
console.log(+y);
// -1

Usage with non-numbers

js
+true  // 1
+false // 0
+null  // 0
+[]    // 0
+function (val) { return val; } // NaN
+1n    // throws TypeError: Cannot convert BigInt value to number

Specifications

Browser compatibility

Desktop Mobile Server
Chrome Edge Firefox Opera Safari Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet WebView Android Deno Node.js
Unary_plus 1 12 1 4 1 18 4 10.1 1 1.0 4.4 1.0 0.10.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Unary_plus