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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语法
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) Unary plus operator |
Browser compatibility
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