When my console throws a NaN I kinda think of it as an Halloween kid receiving a fruit instead of a candy. They won’t say “That’s a fruit”. They’ll say “That’s not a treat”.
I’m personally pissed more often by a falsy 0.
Did you know that early analog computers would literally explode when asked to divide by 0?
Now computers just say “Hey stupid, that shit is not even a Number in a mathematical sense, but sure I’ll add one to it.” instead of “Why would you kill me like this?”
You can’t really define Infinity as a number, yet it is part of their world.
So typeof NaN === ‘number’ totally makes sense in that regard.
If you ever worked with arrays of dates, don’t judge NaN too harshly.
myThing.property = "some string"
if (myThing.property) { // true
// do something
}
It works with everything except of course for falsy values
myThing.number = someNumberThatShouldNotBeEqualToZero
if (myThing.number) {
// do something very important with that number that should not be equal to zero
}
// This can fail at anytime without warning
So you've got to be extra careful with that logic when you're dealing with numbers.
I am not saying it's wrong though. I'm saying it's often annoying.
Besides, null is a perfectly valid value for a property, just as 0. Working with API Platform, I couldn't tell the number of times I used this kind of statement:
if (property || property === null) {
// do some stuff
}
Probably just as much as
if (property || property === 0) {
// do some stuff
}