How to strictly judge NaN in JavaScript

Delete all false values ​​in the array.

In JavaScript, false values ​​include false, null, 0, "", undefined and NaN.

For NaN judgment, JS provides the function isNaN(). However, using the isNaN() function can only determine whether the variable is non-numeric, but cannot determine whether the variable value is NaN.

So, applying the properties of NaN:

> NaN === NaN;
false //永远返回false

We can use === to determine whether the variable is NaN. You only need to determine whether the variable is equal to itself. If not, the value of the variable is NaN.

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