Why Does JavaScript Treat 0 and -0 as Equal Despite Their Distinct Representation?

Inquiring about the Nature of 0: Are 0 and -0 Identical?

The ECMAScript 5.1 specification has defined 0 and -0 as distinct entities. This raises the question: why then does 0 === -0 return true?

IEEE 754 Unveils the Existence of Signed Zeroes

JavaScript employs the IEEE 754 standard to represent numbers. The standard introduces the concept of "signed zero," where both -0 and 0 are recognized. It's a variation of the extended real number line, allowing for the existence of different interpretations of infinity (1/−0 = −∞ and 1/ 0 = ∞).

Theoretical Distinction, Practical Equality

While 0 and -0 are theoretically distinct in Javascript's representation, the Strict Equality Comparison Algorithm in section 11.9.6 explicitly mandates that 0 and -0 are considered equal for comparison purposes. This decision was made to simplify coding and avoid unnecessary complexity.

A Note on Object.is

With the introduction of ES2015, a new comparison method was introduced: Object.is. It explicitly distinguishes between -0 and 0, as in Object.is(-0, 0); // false. However, this method is generally recommended only for specific cases where the distinction between signed zeros is crucial.

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