一个变量与自身比较 [英] Comparing a variable with itself

问题描述

我绊了这种填充工具Array.prototype.includes的。
<一href=\"https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes\">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes.
是否有变量与自己对线21,22比较的原因是什么？

 如果（searchElement === currentElement ||
         （searchElement == searchElement和放大器;！＆安培;！currentElement == currentElement））{
  返回true;
}
 

解决方案

是，这第二个操作数的 || 并检查是否既 searchElement 和 currentElement 是的 NaN的 - 的的仅在JavaScript值不是 === 本身。 包括应该使用的的 SameValueZero 的等价算法，这是从的的 全等比较算法的（使用<一个href=\"https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Identity\"相对=nofollow> === ）或的 EM> SameValue 的算法（中的 Object.is ）。

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;
}

解决方案

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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