将变量与自身进行比较 [英] Comparing a variable with itself

问题描述

我偶然发现了这个 Array.prototype.includes 的 polyfill.https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes.21,22行的变量和自己比较有没有道理?

I stumbled over this polyfill of Array.prototype.includes. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes. Is there a reason for the comparison of the variables with themselves on line 21,22?

if (searchElement === currentElement ||
         (searchElement !== searchElement && currentElement !== currentElement)) {
  return true;
}

推荐答案

是的，|| 的第二个操作数确实检查了 searchElement 和 currentElement 是 NaN - JavaScript 中的 唯一值 不是 === 给自己.includes 应该使用 SameValueZero 等价算法，区别于严格相等比较算法(由 ===) 或 SameValue 算法(用于Object.is).

Yes, this second operand of the || does check whether both searchElement and currentElement are NaN - the only value in JavaScript that is not === to itself. includes is supposed to use the SameValueZero equivalence algorithm, which is different from the the Strict Equality Comparison Algorithm (used by ===) or the SameValue algorithm (used in Object.is).

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