[lmkg]

I think there are a few cases of non-transitive equalities in JavaScript, specifically around falsey values. Part of it also has to do with whether x is the right-side input or the left-side input, because that changes type coercion rules.

Aha, found one:

  ['0'] == 0
  > true
  [0] == 0
 > true
  [0] == ['0']
 > false

Transitivity of equality can also never be relied upon when dealing with Floating Point numbers. This is correct and unavoidable behavior, but still surprising to many developers.

[gsg]

That's not due to transitivity: ['0'] == ['0'] (and for that matter, ['0'] === ['0']) is also false. These operators compare objects for identity, not structural equality.