javascript - Why is NaN === NaN false?

Question

This question already has answers here:

Answer 1

Strict answer: Because the JS spec says so:

• If Type(x) is Number, then
  • If x is NaN, return false.
  • If y is NaN, return false.

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Useful answer: The IEEE 754 spec for floating-point numbers (which is used by all languages for floating-point) says that NaNs are never equal.