The + operator precedes its operand and evaluates to its operand but attempts to convert it into a number, if it isn't already.
The + operator precedes its operand and evaluates to its operand but attempts to convert it into a number, if it isn't already.
+x
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.
const x = 1; const y = -1; console.log(+x); // 1 console.log(+y); // -1
+true // 1 +false // 0 +null // 0 +[] // 0 +function (val) { return val; } // NaN +1n // throws TypeError: Cannot convert BigInt value to number
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| 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 | |
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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Unary_plus