SameValueZero

SameValueZero is a comparison algorithm used in JavaScript, primarily within the `Map` and `Set` data structures, and the `Array.prototype.includes()` method. It's designed to determine if two values are the same, with specific handling for certain edge cases.

Unlike strict equality (`===`), which treats `NaN` as not equal to itself, SameValueZero considers `NaN` to be equal to `NaN`. This behavior is crucial for `Map` and `Set` to correctly store and retrieve values that are `NaN`. For instance, if you were to use strict equality with a Map, adding an entry with `NaN` as a key and then trying to retrieve it using `NaN` would fail. SameValueZero resolves this.

Another distinction from strict equality is how it handles `-0` and `+0`. Strict equality considers these two values to be equal. SameValueZero, however, treats them as distinct. This means that in the context of `Map` and `Set` operations, `-0` and `+0` can be treated as separate keys or elements.

In summary, SameValueZero provides a consistent way to compare values, ensuring that `NaN` is always considered equal to itself, while distinguishing between positive and negative zero. This makes it a more robust comparison for certain programming scenarios, particularly when dealing with collections or checking for the presence of specific elements.