# JavaScript: Negative Zero (-0)

In JavaScript, negative zero `-0`

is not the same as a positive zero `+0`

.

This is because numbers in JavaScript are represented using the IEEE 754 floating-point standard which requires zeros to have an associated sign. Floating point numbers include a sign bit (0 for positive, 1 for negative). In the case of `+0`

, the sign bit is 0 while in the case of `-0`

the sign bit is 1.

## How does JavaScript handle comparison?

```
+0 === -0 // true
-0 === +0 // true
```

This is because of ECMAScript's *Strict Equality Comparison Algorithm*:

If Type(x) is Number, then

a. If x is NaN, return false.

b. If y is NaN, return false.

c. If x is the same Number value as y, return true.d. If x is +0 and y is −0, return true.e. If x is −0 and y is +0, return true.

f. Return false.

## How to distinguish between the two?

Object.is() can be used:

```
Object.is(+0, -0); // false
Object.is(-0, +0); // false
```

## How are strings handled?

Both +0 and -0 will return "0".

```
const negativeZero = -0;
negativeZero.toString() // "0"
const positiveZero = +0;
positiveZero.toString() // "0"
JSON.stringify({"negativeZero": -0}); // '{"negativeZero":0}'
```