javascript - 同值零算法如何工作？

Question

我正在浏览 Javascript.info 中的 map 章节，并且有一个指向 SameValueZero 算法的链接。谁能用简单的语言解释一下该算法是如何工作的。

我尝试浏览链接但找不到任何内容。

Answer 1

参见 specification :

The internal comparison abstract operation SameValueZero(x, y), where x and y are ECMAScript language values, produces true or false. Such a comparison is performed as follows:

1. If Type(x) is different from Type(y), return false.

2. If Type(x) is Number, then

   • If x is NaN and y is NaN, return true.

   • If x is +0 and y is -0, return true.

   • If x is -0 and y is +0, return true.

   • If x is the same Number value as y, return true.

   • Return false.

3. Return SameValueNonNumber(x, y).

它与 === 测试基本相同，除了当 x 和 y 都是 NaN，他们也通过了测试。你可以这样实现它:

const sameValueZero = (x, y) => x === y || (Number.isNaN(x) && Number.isNaN(y));

console.log(sameValueZero(0, 0));
console.log(sameValueZero(0, 1));
console.log(sameValueZero(0, NaN));
console.log(sameValueZero(NaN, NaN));