-1

I want to test if the result of an operation (or a number) is Negative Zero (-0).

Doing a comparison using == or === does not work because:

0  == -0     // true
0 === -0     // true

I have considered that a number divided by -0 will give -Infinity; so if say 1 is divided by the number to be tested results in -Infinity, then the input number was -0.

1/number == -Infinity;   // true if number is -0

Is this a valid and sound/correct method to do the test; or is there an alternative better way for testing?

Also, is there any other number (other than -0) if 1 / number will also give -Infinity? Therefore the necessity for testing first that the number is zero before the check is made that it is -0. i.e. as follows:

number ==0 && 1/number == -Infinity;

Thanks

function isMinusZero(number) {return 1/number == -Infinity;}


// ========= Test Cases ===================
console.log(isMinusZero(-0))              // TRUE
console.log(isMinusZero(-0-0));           // TRUE
console.log(isMinusZero("-0"));           // TRUE
console.log(isMinusZero(55/-Infinity));   // TRUE (Number divided by -Infinity is -0)

console.log("--------------");

console.log(isMinusZero(0));              // FALSE
console.log(isMinusZero("0"));            // FALSE
console.log(isMinusZero(4));              // FALSE
console.log(isMinusZero(-Infinity));      // FALSE
Mohsen Alyafei
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2 Answers2

5

Object.is will give you what you want:

const theNum = -0;

console.log(Object.is(theNum, -0));
console.log(Object.is(0, -0));
CertainPerformance
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-3

Try giving -0 as string

'0'  == '-0'
Yogeshwaran
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