javascript - [] 与 [] 不同

Question

我被要求用 Javascript 编写一个函数 sortByFoo 来正确响应此测试:

// Does not crash on an empty array
console.log(sortByFoo([]) === []);

但我尝试过一些事情:

[] === [];
>> false

所以我可以确定，无论 sortByFoo 函数如何，这样的测试总是会失败，不是吗？ 但我想解释为什么会发生这种情况。为什么 [] 不等于/等于 [] ？

请原谅我的近似英语，这不是我的母语:p

Answer 1

如果您查看 javascript/ecmascript 的规范，特别是 section 11.9.6 ，您将看到如何与 === 进行比较。

The Strict Equality Comparison Algorithm

The comparison x === y, where x and y are 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 Undefined, return true.
3. If Type(x) is Null, return true.
4. If Type(x) is Number, then
   • If x is NaN, return false.
   • If y is NaN, return false.
   • If x is the same Number value as y, return true.
   • If x is +0 and y is −0, return true.
   • If x is −0 and y is +0, return true.
   • Return false.
5. If Type(x) is String, then return true if x and y are exactly the same sequence of characters (same length and same characters in corresponding positions); otherwise, return false.
6. If Type(x) is Boolean, return true if x and y are both true or both false; otherwise, return false.
7. Return true if x and y refer to the same object. Otherwise, return false.

由于您的数组一直到第七步，因此它们必须是同一个对象，而不仅仅是两个相同的对象。常规相等运算符 (==) 也是如此。