The most perspicacious among you will have realized that "associativity" is not at all the right word to describe what I meant! :)
Javascript actually has non-associative operators, like the exponentiation ** operator:
(a ** b) ** c !== a ** (b ** c).
What I did meant is that the operator behavior changes based on where it is called, but I'm not sure there is a term to describe that. But for sure, this is not "associativity"! :)