> I think you should rather think harder, learn math possibly

Oh the irony, when stating that 1/0 = infinity. If you'd learn maths yourself, you'd know that 1/0 is undefined.

yea 1/x is not strictly defined for x=0, but you can extend it in ℜ ∪ {+∞,-∞}, I don't know your math background, but 1/-0 could make you think of limits:

1/0 is like 1/0⁺ (limit of 1/x in ]0,+∞[ when x->0) == Infinity.

1/-0 is like 1/0⁻ (limit of 1/x in ]-∞,0[ when x->0) == -Infinity.

1/Infinity is 0 ....

0/0 is however an indefinite form, so it's NaN

so the behavior of JS makes sense

And even if 1/0 and 1/-0 returned NaN, they wouldn't be equal to each other too

I'm not sure that's right. 1/0 is undefined NOT infinity, hence -1/0 is also undefined. So actually line 3 should evaluate as true.

NaN === NaN evaluates to false. That’s what happens here, not anything with Infinity.

Yeah, that makes sense mostly. But why is NaN === NaN false? What am I missing here?

Because there is many ways NaN can be generated, all very different.

== is only defined for numbers, too.

1/0 and 50/0 aren’t the same, for example.

just type them in your console instead of saying wrong things

Then they don’t conform to the IEEE standards, and the Javascript implementers are wrong.

NaN !== NaN is just right

Yes, but 1/0 === Infinity isn’t. That number is very different from Infinity.

Object.is(a,b) end of story

no, -Infinity is not Infinity